I wanted to throw my twopenneth worth in.
To begin with it was definitely #3, it was sexual. Seeing my legs in nylon and my other bits in lingerie was a thrill and can still be, but it has become far more than that. In fact the sexual pleasure I derive is now not the point at all, although my wife cannot quite get that. For her it must be about sex, yet I very quickly realised something else was happening and it increasingly became #1. Women’s clothes are so much nicer, they feel better on, they are pretty and make me (at least) feel attractive even if in reality I am not.
As for #2 I don’t feel like a women in a man’s body, but I do feel like a man who is sometimes so feminine ‘he’ wants to present as ‘she, because a part of me is she. When I am Natasha I am a women, when I am in drab I am a man.
So for me a mix of all, but it is most about releasing the inner feminine part of me. I feel like a women when I slip a skirt or dress on, even though I don’t look it. I like the female part of me, it is gentle and more considered. It has more class or style. I find my mannerisms, ways of moving and even my words change automatically to become more feminine.
No idea if that has answered the question, but it does help me putting it out there.