Sorcerers don't have many spells. If I compare them to other full casters (I'm not including Warlocks in this because they work entirely differently), namely Bards, Clerics, Druids and Wizards, then they seem to come up short.
By level 20:
- Bards know 22 spells;
- Clerics/Druids can have between 24-25 spells prepared (assuming WIS of 18-20);
- Wizards know a whopping 44 spells (only including spells gained via levelling) but can only prepare about 25, as per Cleric/Druid;
- Sorcerers only know 15;
Sorcerers are the clear losers here. Not that I expect them to have as many as Wizards (since that's their thing), but 15 just seems way too few to me, and I don't think that Metamagic alone makes up that difference (which is all they seem to have besides spells). So I was thinking of giving them a free (but specific) spell between spell levels 1st-5th, much the same as I did for the PHB Rangers.
This way, the Sorcerer would know 20 spells; still fewer than everyone else, but not by as great-a-margin. As with my other question, the spells I have picked suit their flavour and include spells from within their own spell list and from other spell lists (which would count as sorcerer spells for them), but only one extra spell per spell level (up to 5th). I'm not listing them all here, though, as it would take up too much room (I've done this for the UA archetypes, too).
I suppose the player of these "enhanced sorcerers" could potentially swap out the free spell for any old sorcerer spell, effectively giving them 20 total spells without the flavour, but as covered in this question, I'm going to assume they can't do that, much the same as with the extra Ranger spells (or at the very least, I would rule that they can't, given that I'd be the DM in this situation, what with it being my homebrew).
So, my question is does the increase in number of spells known impact the strength of the class in a way that might make it preferable to the other spellcasters? I've always felt they were the weaker option, but that might just be because I don't use Metamagic to it's full potential or something, so will these additional spells and the increased flexibility they provide unbalance anything beyond what I have anticipated?
As a caveat, I'm aware that the XGTE archetypes (and the new Giant Soul Sorcerer archetype from UA, but I don't care as much about that because it's just UA, and my main balance concerns are with the official released archetypes) already include an additional spell; namely the Divine Soul's Divine Magic feature (XGTE, pg. 50):
In addition, choose an affinity for the source of your divine power: good, evil, law, chaos, or neutrality. You learn an additional spell based on that affinity […]
and the Shadow Sorcerer's Eyes of the Dark feature (XGTE, pg. 51):
When you reach 3rd level in this class, you learn the darkness spell, which doesn't count against your number of sorcerer spells known.
Therefore, RAW, these Sorcerers would know 16 spells in total by level 20. I'm planning on not giving Divine Soul sorcerers an extra level 1 spell or Shadow Sorcerers and extra 2nd level spell, so that their total is still 20 known spells by the time they hit level 20. I personally don't think this matters too much since it's only one spell's difference, and their class features do provide them with other benefits, so it's not like I'm taking their class features away from them and giving them to every other sorcerer archetype.
I thought to mention this in case this impacts balance, and therefore any potential answers, in a way I haven't anticipated; but this is an aside, just some extra information, and my question is not specifically about this aside, but about the impacts of having any sorcerers with 20 spells.
Best Answer
It will make them stronger, but not much
This answer is about Wizards, but I agree that more spells from the same list are not much improvement. Usual Sorcerers take the 15 spells1 they find best or strongest, so by definition the next 5 will be weaker.
They have the same number of slots, and more importantly, the same number of actions per encounter.
Example: Lightning Bolt
In most situations Fireball is better than Lightning Bolt, as it usually covers more area. It effects more enemies, so most Sorcerers only know the former as they can't afford both.
After this change they might be able to take both, but in the vast majority of the cases, they will still chose Fireball to cast. Only in the few times when the enemy is lined up nicely, or is resistant/immune to fire but not to lightning, will they cast Lightning Bolt. So in about 10% of encounters, they will not lose 50% of their damage (they will lose some damage, as most likely less enemies fit into a line than a sphere).
This comes up to 5%, hardly unbalancing2.
Spells from other lists
This is where the idea can go wrong, so you have to examine it on a case-by-case basis:
A twinned Tasha’s Hideous Laughter or heightened Evard's Black Tentacles3 is very powerful, but no metamagic will make Flame Blade great.
This just can't be answered unless we see the whole list for all archetypes, but than it might be too broad.
Try to fit all possible metamagics on the spells, and if it still does not look overpowered, you are fine.
1. Sorcerers know 15 spells on level 20.
2. The difference is even less, you could just cast something completely different like Toll the Dead or Haste.
3. I think named spells (Evard's, Tasha's) are usually created stronger, because they are unavailable for Sorcerer's. Consider them a Wizard class feature compensating for no metamagic