How to make transformation a truly interesting and erotic experience is one of the central dilemmas of CoC/TiTS, and it's one I've gone back and forth on a lot over the years. In TiTS, Fen arrived at one extreme at how you can provide the experience to your players: You give them a huge amount of personal customisation, all relatively easy to access, each with their own fun description of what takes place - but that's it. Beyond a few bespoke experiences like The Treatment, what you are and what you've become has almost no bearing on your interaction with the rest of the game. Although I haven't spent much time with CoC2 I believe broadly the same is true there, because sadly TFing is something that has never interested Savin. It is unavoidably disappointing, and leaves the player feeling that their choices don't matter, which is the one illusion you never want to disspell in an RPG.
The problem of course is that making transformational content meaningful is very challenging, and necessarily means you will lose out in other areas. Most TF erotic games are very focused (usually on feminisation) because of this. Something on the scale of TiTS is not really feasible.
Something I would bring up here though, as uncomfortable as it may be to do so, is that a lot of TiTS' content is pretty worthless. One off sex scenes you can have with vendors or half-assed OCs that don't develop into a meaningful relationship. One off sex scenes with hostiles that have no impact or development. In TiTS it often seems as if you can have sex with anyone, and it feels empty because most of it doesn't matter - mirroring the TF experience, not coincidentally.
To be clear I like mindless and impulsive sex. I love writing orgy scenes! But done well such content is used to convey something about the location and people it takes place in and with, as well as gratifying the reader. Players want sex that feels part of a grander narrative, that feels earned and risky. When it comes time to create TiTS' heir, I truly hope the fact that transformation has to feel meaningful to be worthwhile is part of its core values.