Doing it:
Of the two? It would be femDiluc.
Other than that? Lisa looks like some who would do a great job at pegging. Charlotte, she would be like "let's try something new!" And then go on to fuck the ever loving shit out of who ever is bottoming.
Receiving it:
Kaeya obviously, he is a anal whore (lovingly) if it doesn't hurt it's not good enough.
I think Venti would let you do it as well.
Wanderer would glare but ultimately enjoy it.
I kinda see Thoma being down for it too. He'd be like "sure if you want to try it..." And then make the lewdest noises...