Yeah, in regards to Aterion, counting him as an elf...idk about that. He might be an elf, but being an elf isn't even tertiary in regards to his character. He doesn't come off as culturally elven or have any particular outlook on life you might connect to being elven. Even the elven longevity thing doesn't seem particularly relevant, since he's already an immortal vampire.

He pretty much could just be another human and nothing would change about him.

Shadowheart's half-elven-ness comes up like once.

If you compare that to BG II, for example, it's radically different. Species and cultural background were pretty defining. I hope with Minsc we can talk to him about his Rashemi culture. Aside from the Gith, everyone seems sorta 'default generic culture' Like an afterthought or something.