I dont really know, this would be more question for Niara, or some other tabletop expert.
But from what i gathered, Tieflings should have option to look almost like Human ... wich they quite clearly lack in Baldur's Gate 3 ...
While Aasimar should look almost like human in default, with some subtle features like feathers in hair, eyes, hair or/and skin that seems to be slightly glowing etc. and they can indeed spread wings aswell, but they are not physical wings like angels, just some translucent incorporeal wings ... dunno how far i am with this, but i imagine it kinda like wings Angels in Diablo have.
