What about things like kegels/squeezing?
Mouths are probably pretty different right? More tongue movement, unless you are facefucking.
If you’ve ever participated in something like a train - can you feel the difference between a vagina that has already been fucked?
Yes, ass is tighter around the opening. Depending on how strong the muscles are, you can feel squeezing. Ass squeezing is more noticeable than vagina squeezing ime.
Mouths are very different.
No real difference in a vagina that’s already been fucked unless it’s getting drier from all the friction but just use lube and it’s fine. An ass that’s already been fucked isn’t quite as tight, but that’s a good thing because you want the ass to be a bit more relaxed and the start is a bit of work to make sure the other person is relaxed enough so you don’t hurt them.