Do girls pee from their butts?
No, they urinate from a hole between the clitoris and the vagina.
There's really no difference. You would talk to them just how you would talk to any other girl. Girls with big butts already know they have big butts. It's only a matter of way you talk to them. For instance, you never disrespect a girl by telling her how big her butt is unless it's someone your comfortable with. Girls with big butts are normal girls.