I would say gooning. It’s basically masturbating without cumming as long as possible. The goal is to stay in the pleasure as long as possible, without restrictions, and just enjoy it. I usually end up being unable to stop myself from cumming which is such a hot fucking way to cum. It’s something I did as a teenager, way before I ever heard the word, and I’ve recently rediscovered it. I like it a lot because the amount of pleasure you get is way higher than just going straight to cumming. I’ve started to explore doing it with a partner during sex and mmmm does that feel fucking good. Not masturbating during sex but just fucking as long as possible and really enjoying the moment and stretching it out. It feels like the right way to fuck and masturbate.
I too fantasized about being with a trans woman. I hooked up with one and I loved it. Later I figured out I’m trans myself. I still fantasize about being with trans women, but now it’s gayer. I would say don’t worry about it too much. Just treat trans women like any other woman, like an autonomous person with their own wants, needs, desires, and traumas (just maybe some more traumas than average). As with any other relationship, when in doubt, ask.