Strictly better? No.
One of the major points of Disguise Self is that it can not only alter your appearance (via illusion), but your clothing and equipment as well.
It's important to note the inverse of this: Alter Self does not specify that it modifies your clothing or equipment. This means that, depending on how severe your alterations are, you may no longer fit into your armor and your clothing may clearly no longer fit you, depending on how simulationist your DM is on the topic. This is especially important if using the "Variant: Equipment Sizes" rule on PHB p.144:
In most campaigns, you can use or wear any equipment that you find on your adventures, within the bounds of common sense. For example, a burly half-orc won’t fit in a halfling’s leather armor, and a gnome would be swallowed up in a cloud giant’s elegant robe.
The DM can impose more realism. For example, a suit of plate armor made for one human might not fit another one without significant alterations, and a guard’s uniform might be visibly ill-fitting when an adventurer tries to wear it as a disguise.
Using this variant, when adventurers find armor, clothing, and similar items that are made to be worn, they might need to visit an armorsmith, tailor, leatherworker, or similar expert to make the item wearable. The cost for such work varies from 10 to 40 percent of the market price of the item. The DM can either roll 1d4 × 10 or determine the increase in cost based on the extent of the alterations required.
Even if your equipment does fit you after the effects of the spell, any well known gear or accessories may still let you be identified, especially if they're more well known then your actual physical attributes.
There are a few other considerations as well.
One of them is that both Alter Self and Disguise Self can be used at the same time, to enhance the illusion with actual physical changes underneath it. Do note that this is only possible because Disguise Self does not require concentration, which is another point in its favor over Alter Self, which does. This means Alter Self can fail earlier than intended (especially in combat or while under stress), while Disguise Self will last the duration under most conditions, and still allows you to cast other concentration spells.
Another is comparing how Disguise Self and Alter Self interact with height & size.
Alter Self actually changes your height, while Disguise Self only creates the illusion of a height change, keeping you your usual size. This might matter if your DM actually cares about character height in certain situations rather than just your size.
In addition, Alter Self restricts you to only changing your appearance to a creature of the same size with no other restriction on maximum height gain/loss, while Disguise Self only has a restriction on height change rather than size change.
For example, with Alter Self, you could change the shortest possible dwarf into the tallest possible goliath, whereas with Disguise Self, you could make a dwarf appear to be a halfling (so long as you're not trying to change your height by more than a foot in doing so).
Overall, I'd probably rate Alter Self better than Disguise Self in some combination of the following situations:
- There is plenty of time to make preparations in advance, including having an appropriate alternate outfit ready.
- You are unprepared, but you only need minor superficial changes with no drastic change such as size, making the lack of alternate costume not an issue.
- You are in no danger of having your concentration broken for the next hour, nor are you likely to need to cast any other Concentration spells.
- You are likely to be thoroughly inspected for some reason or another.
In other situations, there is a chance Disguise Self may be the more appropriate spell. In a situation requiring an emergency drastic appearance change (clothes, size, and all), for example, I would much prefer Disguise Self as my option.
The simple answer is you only get to use one other source material book, beyond the PHB, for everything related to your character creation (and advancement). So no, you can't have a Zariel tiefling as a Conquest Paladin.
Per the ALPG v9.1:
Forgotten Realms characters can choose race and class options from the Player’s Handbook and one other resource—a rule called “PHB+1.”
Since you want your class to be the Paladin's Oath of Conquest, which comes from Xanathar, all other creation choices (except where spelled out) such as your race MUST come from either the PHB or XGtE.
For the the second part, the bulleted list refers to variants that are allowed.
- Variant Human Traits (PHB)
- Since everyone gets the PHB, anyone can use the variant human traits
- Half-Elf and Tiefling Variants (SCAG/ToF)
- If SCAG or ToF is your +1, then you can use the variant versions mentioned in that source
- Option: Human Languages (SCAG) (3)
- Optional Human Languages are mentioned in SCAG, but (3) says you can take this even if SCAG is not your +1
- Blessing of Corellon (ToF) (3)
- Even if ToF is not your +1, you can still apply the optional Blessing to your elf
It's a really horribly worded doc, and it gets worse every revision as they try to shoehorn in new rules to existing text. Such as, in previous versions of the doc, they specifically called out variants and optional play were not allowed. But then they realized that feats and multi-classing are listed as optional and therefor technically are against the rules. So they took that out, but didn't fix surrounding text.
Best Answer
Yes. It all depends on your imagination. Your alter ego could always wear a large hat that he never removes. Or he could always wear a hood that hides his face with the reason being he was burned badly fighting a black dragon etc. If he is wearing MC Hammer pants (or just really baggy clothing) he could wrap the tail up around his midsection and look like he has a gut. This may impair his walking, but that would become part of the persona. No where in the book does it say you get disadvantage on disguise checks based on your race. (if I misspoke here I hope someone will correct me). Also, you get to describe how your horns look, so you could talk to your DM about letting yours be a little smaller than average.
The only low level spell I can think of is Disguise Self, but you don't get that as a warlock.
There is a magic item called The Hat of Disguise, but you would have to get that as a boon from your DM since I can't think of any other way a 1st level character would have access to it.
One other point is that it took time and money to create this persona. Maybe out of game, but it is considered that it was done this way. So now instead of getting suspicion, you get "Oh, that is just old Brennar, he's always like that". And "I saw his face once (or you could have paid someone to spread the rumor) and you don't want him taking off that hood".