Tropes are literary devices - not so much genres in themselves but literary plot devices or motifs. In TG fiction, there are numerous - there are probably at least half a dozen ways in which the victim can be trapped - one of the most common is "caught in the act", but there are other stories where the proverbial "point of no return" is reached with the victim still dressed in male clothes - perhaps she's secretly recorded his crossdressing, or has printed off the stories he's been submitting to TG sites or his online role-play sessions. Away from forced fem, intersex is a fairly common one - the protagonist believes he's TG, but a medical examination reveals the character's actually a fully-functional girl, albeit with a slight reconfiguration of the genitals. Hair removal creams that permanently kill the hair follicle with very little pain within 10 minutes are also fairly common in TG literature.

In terms of more general tropes, one of the most commonly used is "Lampshade hanging": something completely unbelievable happens. So how do you maintain suspension of disbelief? You draw attention to it, in the form of the characters not believing what's going on either! Then there's the "Shout out", a thinly veiled reference to another work of fiction. Paritcularly in fan fiction, you may encounter the "Author avatar", a character that looks suspiciously like an idealised version of the author - taken to extremes it could turn into the dreaded "Mary Sue" - a side character that pops up out of seemingly nowhere, is incredibly beautiful, and solves the problem / kills all the enemies etc. while the supposed heroes just look on and do nothing.