If you are asking for which ones are in the game, it is quite a lot. The whole cast has a few specific tfs not shared with the others, but they all can be transformed in some way.
I think every character has a gender transformation (MtF and FtM), with some of them being more fleshed out than others (example: one character can become a princess later on if MtF'd). A few characters have breast expansions, and one even has cock expansion.
You can also change a character's race to one of the other races (dog people, cat people, and reptile people). Each character has a unique form for whichever race they belong to.
As for other types of tfs, there is weight gain, muscle gain, princessification, mind altering, pregnancy (via magic and non-magic means), sissification, and even a rather silly one that I don't want to spoil. Characters can undergo multiple transformations, so the idea is to expirement around and see what you can do. I hope this helps!