Yeah I think you might have just needed to figure yourself out, I think unless you're super straight or in denial, everyone at least contemplates about having sex with both genders to some degree. If you ultimately settled by 20 then I think it was purely just you trying to get through that teenage phase.
You remind me of myself in a few ways and ultimately I agree with everything you've said, though I personally believe for some people you can find happiness and peace with transitioning at least in theory. I know a very small handful who've successfully transitioned and stayed that way. Personally the way I see it is the thing most people forget it the transition part involves you know transitioning.
I've met people on both ends of the transition train who are mostly chill and then the people who I swear didn't transition at all because they have to add the "trans" part for no reason. It baffles me because I'd think people would want to just be their gender and end it there, but people really cling to that label way too much. My closest friend is someone who intends to transition and while I am skeptical of if it'll work out the way they want, I know she ultimately wants to do it no matter what and would rather have that then stay as is.
The thing me and my friend both agree on is that if we were to transition, we'd want to drop the "trans" in trans woman as much and as fast as possible. Because we ultimately want to just be the end result we think we should have been, the "trans" to us is an identity that doesn't need to exist publically once you've transitioned. If trans women/men are just women/men, then that is what it should be in the end. Trans an identity that is just a means to an end, it is not who you are forever unless you want to get really technical, but you don't need to live life in technicalities 24/7 over stuff like this. Just be a woman if you want to be a woman.