The exact break down of Perform subskills is largely up to the table. Most players just pick one Perform skill and stick with it, because that saves skill points; the different subskills are just so you can pick exactly what you are doing. Some players pick more than one for a few reasons, which I’ll get to, but the short answer is, “the rules pretty much assume you’re only using one Perform subskill at a time, because the rules don’t really care that much about Perform.”

Perform isn’t actually that important

The uses of the skill are for making money and earning a name for yourself performing. However, most D&D characters are adventurers, who will have little opportunity to use Perform in such a fashion, and regardless, adventuring pays far better and is much more likely to result in power and influence (assuming you don’t die, of course).

Furthermore, bards don’t actually need to do well on their Perform checks to use Bardic Music. They need a minimum number of ranks (more on that in a bit), but once they have those it doesn’t matter how well they do on their actual check. And since Inspire Courage is by-far the most important Bardic Music effect, and only requires 3 ranks, depending on what you do with your career (i.e. maybe you multiclass or take a prestige class and don’t get the higher-level Bardic Music effects), you may not actually need more than that.

Thus, having ranks in Perform is almost more of a “backstory” tax – if you want to claim that you are an excellent performer, you need to spend the skill points backing that up. Since it’s a matter of who you are and what your backstory is like, the choice of Perform skill(s) is very much tied to your character and up to you. As such,

There is no canonical list of Perform subskills

The rules themselves occasionally reference Perform subskills – a magic harp that requires Perform (strings) perhaps, or a prestige class with ranks in Perform (dance) as a prerequisite. They can occasionally get very specific (there’s at least one book that has special rules for Perform (weapon drill), and a certain notorious third-party book includes rules for Perform (sexual act) – no, I am not joking). But for the most part, the rules don’t really care which Perform skill you have, and never lists any kind of canonical set.

Most tables¹ are fine with you picking any kind of Perform you want to make up

Since there aren’t any official Perform skills, and it doesn’t really matter, most tables are fine with you defining your Perform skill however you want it, so long as you state what instrument(s) you use to perform it. A masterwork instrument provides a +2 bonus, but since you can only get the bonus once, it’s usually best to stick to a single instrument rather than have something like Perform (one man band) that requires a whole set, but you can if you want (and your table agrees; in my experience it’s not a problem).

A lot of players just pick Perform (sing) or Perform (dance) just so they can never be stripped of their ability to perform by the loss of an instrument (but see summon instrument for an easy fix to that). A masterwork tambourine (or similar) is sometimes used to get a +2 bonus on Perform (dance), and to qualify for the requirement that allies be able to hear your performance for Bardic Music, but talk to your DM about that before using it.

Having multiple Perform subskills is usually seen as a redundancy

Now, redundancy can be a good thing. For example, if you lose your instruments but someone lends you a flute, it would be nice if you have Perform (wind instrument) as well as Perform (strings). Plus, as I mentioned, sometimes magic items want a particular subskill, so if you want to use both a magic flute and a magic drum you need both Perform (wind instrument) and Perform (percussion instrument).

But unfortunately, the rules also see multiple Perform subskills as a redundancy. There are no rules, to my knowledge, for one person using multiple Perform subskills as a part of a single performance, even though that is a really common thing for musicians, e.g. Perform (guitar), Perform (sing), and Perform (dance) for your average frontman.

As a result, there’s not really a lot of reward for having more than one Perform skill unless you think you’re likely to find yourself required to use a particular instrument that isn’t your top choice. Most people pick just one for that reason.¹

But if someone did take several Perform skills, personally, I would rule that the lower rolls were Aid Another (...Aid Yourself?) attempts on the highest roll, so you get a +2 bonus for every additional Perform subskill you integrate into the performance and roll at least a 10 on. Alternatively, you could be ruled as making three separate checks at once, thereby potentially multiplying your monetary reward as well as your chances to be noticed by important people. But the rules don’t specify either of these.

Bardic Music requirements

Bards must have at least one skill with the minimum number of ranks listed in Bardic Music effect in order to use it. So yes, you need at least one Perform subskill with 3 ranks in order to use Inspire Courage; having one rank in each of three Perform subskills will not be sufficient.

Note that none of the Bardic Music effects actually involve rolling a Perform check; you probably will for the sake of determining how nice it sounds, but even if you do terribly the magic still works.² As a result, strange as it may sound, Perform isn’t actually that important to the bard, beyond having the requisite ranks. Using Perform as a skill is very rarely critical; you can earn much more fame and fortune adventuring in most games than you can Performing, and probably will unless the entire table wants to do a theater game (and even then, I’d argue that D&D is very much the wrong system to use for that).

Footnotes

¹ In my experience. Most of the games I’ve played in have challenged the PCs quite stringently, and therefore required reasonably careful choices made in allocating character resources, including skill points. Other tables may find it more common to “waste” lots of skill points on “redundant” Perform skill ranks.

² I once played a game with a Cha 5 orc bard³ who regularly rolled negatives on his Perform checks despite the requisite 3 ranks, thanks to a couple of Perform-weakening flaws; he managed to get like a −4 modifier or something. We had great fun with his singing being terrible and all of our characters trying to get him to stop singing.

³ Yes I did just put a footnote in my footnote, nyah! Anyway, the orc wasn’t actually a “bard” per se, but rather a homebrew class that got Bardic Music like bards do. I mention this because a Cha 5 bard would be a really terrible choice, considering how nice the spellcasting they get is.

I really love to introduce D&D to new players, so I've been through this situation alot. I have played way more games with inexperienced players than with experienced ones. This is how I handle it, usually as the DM.

This is also exactly how I handled it with the specific player I've mentioned in the question - and it worked great. She's the most interested player in my current table and asks every week if we're going to play this week. She loves her Forest Gnome Druid (yeap, I know) and even added a hometown to the Forgotten Realms setting we're playing (LMoP - it was easier to ask her to create a hometown than read every possible place from the FR and decide one where she is born).

Make a group session for creating characters

I usually do this when I have more than one new player. This saves time as I can explain the same things for everyone at the same time, they can learn together, other (more experienced) players can help them as well and personal contact (rather than internet) seems to work better when explaining things. If the campaign needs a somewhat decent party setting, this also brings them together to talk about who is going to do what.

Explain the basics of each class

First thing I do is to explain, very briefly, the classes. I try to focus on how the books describe them, but it obviously is a little biased by how I see each class. Explain them what the classes are better doing (i.e. what they are mostly designed to do. Yes you can build a Tank Wizard, but I wouldn't personally say the class is designed for that) and if possible link them to culture characters. Don't use Gandalf for Wizard. Seriously. Don't. Harry Potter describes better.

After that, ask them for which class(es) they liked more. This step reduces alot of the time needed, as they won't need to read the entire Chapter 3 now.

Note: I prefer to start with the class over the race (contrary to the PHB guidelines on p. 11) because I feel deciding what you do is more important than what race you are, and if you want to make some optimization you will be choosing the race based on your class (or vice-versa).

Quick note on Spellcasters

Note that spellcasting adds a lot of extra details to the class. Prepared spellcasting is even more details. Let them know that spellcasters will require some considerable extra reading. I wouldn't straight-forward say they shouldn't be playing these classes (I've seen people telling new players that they should be playing Rogue/Barbarian/Fighter or w/e) but let them know that they have a harder learning curve. It's their characters and their choices. Don't take it away from them. If the character turns out to be "bad", they actually learned from it.

For challenging campaigns, it might actually be better to suggest a martial class instead, though. More details later.

Explain the basics of each race

How do they look like? What are their main features (Halflings are stealthy and lucky, dwarves are strong and resilient, Tieflings are the sons and daughters of satan, etc)? How are they seen by other races in your world? Try to not talk about mechanical details (this race gets a bonus in these attributes and can reroll 1s) but rather flavor and role-playing features.

If your campaign needs some optimization, recommend them what races fit best with their chosen class. I've highlighted the condition because otherwise let them try out playing that Wizard Dwarf. It could even fit in a campaign that needs some optimization, but usually that will need some experience from the player using that uncommon character, which is the exact opposite of the scenario in the question.

Even if you are not in an optimization scenario, synergy between attributes is part of the flavor. I might not have been clear about this earlier, so, clarifying: you should be explaining them that gnomes and high elves make better wizards than dwarves, which make better fighters and barbarians. You should let them play their Wizard Dwarf if they want to, but make sure they understand their choice and their consequences, make sure they actually know they are making a suboptimal choice, but do not discourage them to do so unless needed by the campaign. As I'll repeat later: This is their characters and these are their choices, the important thing is that you made clear what are the consequences of these choices so they won't be feeling bad later in the game and blaming you for their "bad character", or, as mentioned in a comment, they won't feel "cheated".

After that, ask them which race(s) they liked more. Again, this reduces the amount of reading from Chapter 2 alot.

Attribute Distribution

Now that you have your race and class, it's time to distribute the points in scores. For new players, I usually either roll for scores or use the default array. Explain them briefly what each attribute score influences and which are more important for their classes (according to the PHB). Try to not say "your highest score should be Int for your Wizard" (the PHB does it, and I hate it) but rather on the lines of "Int is the score you will be using for every spell you cast, so it's important". If they still want the highest score to be Dex or Con so their Wizard is more resilient, let them. Repeating: This is their characters and these are their choices, the important thing is that you made clear what are the consequences of these choices so they won't be feeling bad later in the game and blaming you for their "bad character". Obviously, again, this changes if you are running a campaign that needs optimization. Then you should guide them towards the optimal path.

About point buy

Again, that depends on you and your campaign, but unless you are running a challenging campaign that needs some optimization, I think point-buy is time consuming and worries players too much about min-maxing. This is not an experience I want to give them in their first time. Obviously there are players that love min-maxing and optimizing, and in this case they will probably be playing with a DM that likes it as well in a campaign that requires this optimization, which is the reason I'm always stating these scenarios exist and how to handle them.

Background

Yes, I prefer to let them choose/write their background before start filling the numbers. Usually, I ask my players to describe their backgrounds themselves and only point the existing ones if they are having a creative block.

Ask them what they learned to do before adventuring (the 2 skill proficiencies will come up here), what places and races they visited and what they worked with (languages/tool proficiencies). Finally, ask about the character personality itself, explaining the concepts of Traits, Flaws, Bonds and Ideals.

Quickly explain the background features and how they are used to give them Player Agency over the story. By now, with their stories, race and class defined, there should be a few that actually make sense, again reducing the reading they are needed to do.

If this is an optimization campaign, this is where being in a group session helps alot. The players can talk with each other and check which skills each one will fill for the party. If you are open about the challenges they are facing, tell them which skills will be most useful in the campaign. People are usually sad when they get Animal Handling and discover they are in a world where every animal has died - it also doesn't make much sense, since he wouldn't have many ways to actually learn that skill to begin with.

Spellcasting

First thing: I hate how PHB is organized for spellcasting. It's pretty annoying to go from the list your class know to the list of spells where they are actually explained. I use donjon's spellbook instead.

Second, I like to give them a free pass out of jail, as they will probably be choosing spells that seem nice but actually suck.

If you are not the DM or you don't want to do this, let them know which spells are "traps" and which spells won't be useful specifically in your campaign.

This is where things get really tricky for campaigns that need optimization. You will probably have to point a decent optimization guide here. Not only they will need to learn the best choices for their characters, they will need to learn how to use these spells in their best ways. For example, the best use (IMO) of Polymorph is kinda counter-intuitive for most people (hint: it's a buff spell).

Time to fill the numbers

Honestly, I feel like the hard part is gone. Usually the hardest thing for new players is actually choosing from the huge amount of possibilities they have, and that's the part I usually have to help them more.

Now you can redirect them to very specific sections of the PHB - one for their race, one for their class, one for their background feature. That can be done as homework. But if you still have time in the group session, let's keep it going:

First, let's fill the quick things. Proficiency bonus is always the same number (point the table on their classes for that), HP is straight forward for level 1 characters, speed is given by their race. I wouldn't recommend starting from higher levels for new players, but if you really want to, explain how to get their max HP.

From their class, they also get their Saving Throw proficiencies already, so explain them how proficiencies work and how they mark it in the sheet. Since there is no choosing here, you can already explain how to calculate Bonus. If you haven't already done it when explaining the attribute scores, tell them how to translate the Score into a Modifier. The floor((x - 10)/2) formula works fine for me since I play with math people, but you can always point out the table for them.

After that, let's get the equips. Again, show them where they are listed in their Class and in their background. I have the pages for the Armor and Weapons pinned in my PHB, as they are probably the most frequent tables I use. When they have their armor and weapons, they can fill the AC and the Attacks. Now it's a nice time to explain how attack rolls, AC and damage work.

Finally, let them choose from the skill proficiencies of the class. Explain them what each skill (they can choose from, not every skill in the game) helps them to do.

Homework

We have greatly reduced the amount of reading and time they will consume. From my experience, a 2-3hr session is enough for doing all of this and the players leave actually knowing what their characters are. Again, from my experience, they spend a lot more time if they have to learn it alone, reading every class and race and background and frequently don't understand exactly what they are doing.

Now, they have to:

• Read their race section in Chapter 2 and learn their special features. Write them down in the sheet.
• Read their class section in Chapter 3 and check if they have anything else to choose (Fighting style for fighter, for example). Usually I would tell them to read everything up to third level for now, so they can start thinking on their path (as usually you choose your subclass until there). Write down class features you already have (Second Wind for the fighter example).
• Read their Background Feature in Chapter 4 and understand how they can use it in the story to exercise player agency. Write it down in the sheet.

For next sessions (actually playing):

• Read Chapter 7 (Ability Scores/Skills) from p. 175 onwards, so they know better what they can do and what will the DM usually ask for (which roll, I mean). Usually adv/disadv is better explained during the game, imo. The DC part is also a good reading but honestly you can just tell them that or show the table.
• Read Chapter 9 (Combat). D&D is a combat-based game. This is probably the most important chapter in the book and the only I ask my players to read entirely. They will probably not understand many things, but this is fine, they will get used while playing. The important thing here is that they understand the big picture of how combat works (i.e., initiative, rounds and turns) and what actions you are usually allowed to do. Reading this chapter is specially useful so they don't say too many "I attack" phrases.
• Chapter 8 (Adventuring) has a lot of rules that are usually ignored from my experience. If the DM is going to use them, read it, otherwise I would ignore it.
• Appendix A is also very relevant for combat.

And with that, your new players should be able to start playing. This seems alot, but as I mentioned, it's actually a few hours session that saves much time for the people learning and usually gets them more interested in the game than just telling them to read an entire book and come back with a sheet.

Outcome

Just to repeat myself, from the many tables I've played, the outcome of this "explain the basics and let them choose based on their feelings" method, rather than focusing on mechanical explanations, is enough for getting them started and interested. While I've got players that end up disliking their characters, either because after reading the class/race they actually interpretated it in other way than I explained, or just because they thought the character would be different, most of my new players enjoyed their characters and overall playing D&D. Obviously the system itself is great, RPGs are great, but I do think this early interaction to make things easier for them helped alot in that outcome.

Similar to spell selection, if they are too dissatisfied with their characters, I have no problem letting them choose/create another and retcon it.