Is all the corruption/transformation content tied to bad ends or is there an ongoing corruption mechanic?
On the main route, all of it is either tied to bad ends or happens to NPCs that you have to fight. There is an alternate route available after a certain point (I think the earliest is at the end of chapter 2) where you become a master vampire, but there's significantly less content than the main route for now, and won't be getting any more content until the main route is finished (which will be in just one more chapter, though it's apparently planned to be a two-part chapter). One of the bad endings is also an extended, playable ending where you become a lesser vampire and can corrupt some other characters.
As for an "ongoing corruption mechanic", I'm guessing you're referring to the protagonist gradually getting corrupted as the game goes on? I'm pretty sure that's not a thing (though I actually haven't played the last two chapters yet, I haven't seen any indication that's the case), but there is a status effect that you can get that works kind of like poison, and gives you a bad ending if you "die" from it. That's probably not what you're talking about, though. There's also an optional drug addiction mechanic in the latest version, but I'm not sure if you'd count that.