I have in only 1 woman. She wanted to try anal sex. It was a strange experience.
Yes, many times.
The biggest reason is because I'm most likely in a relationship with another woman. I am against cheating.
Other reasons could be: I don't find them sexually appealing (even if they are attractive by society's standards) or on rare occasions I'm just not horny.
Go out of my way to see what kind of panties a random female is wearing? No. That's completely disrespectful. If I see it by accident, no harm done.
If we are speaking about girlfriends/fuck buddies, then yes. I have gone digging into a woman's pants to find out what kind of panties she is wearing - if she doesn't tell me beforehand.