It's, I feel, the closest any characters aside from the Champ get to player-character levels of customization, from what I'm aware of. Like, you can't change his race, but the cock, pussy, tits, and pronouns are practically mix-and-match. Also the cock size and and boob size is customizable, though I'm not sure how customizable. I know you'll at least be able to make the dick half as big, though I don't know what other choices may be. Similarly, tits has some pre-set sizes, but there's multiple presets to pick.
You only get to go through the tf'ing once, because of story reasons which you could see in B's thread, or you can see in the quest once it comes out, but basically, it is a single event, rather than a series of events. I will say, though
that the one doing the transforming is Berwyn, to him/herself, rather than the Champ. B, the one writing it, said that he hoped to present it as Berwyn discovering him/herself, and shaping his body into what makes him happy. Anything, including him staying the same, is simply his choice of who he is. Oh, also, while the tiddy and cock will have customizable sizes, the butt's static.