Mechanically the only "good" thing about humans is that spellcasters use Leather Armor and Shields now. And that has to be the stupidest thing in fantasy RPGs in recent years. Larian reinvents the classic Gandalf style Wizard - by giving them a shield. Ok.
The carrying capacity buff in a game where you teleport items to camp and teleport to traders to sell has to be a joke.
Instead, give them that skill and a half-feat already.
Githyanki are stupidly OP with their numerous abilities including skill proficiencies in practically everything on top of teleport abilities and best proficiencies.