Basically, normal enemies will just sort of have their way with you, and then that's it, everything happens in-game, and you retain any effects from it. On the other hand, there will be CGs for anything that implies that the protagonist's journey ended.
I'll also take a shot at animating them with bone-based/deform animation, as a sort of compromise. While I dislike bone based animation for gameplay, I think it's fine for CGs, and better than still-frames. It doesn't really take much work, either, when it comes down to it. I'll be using anime studio, since it can deform raster images.
As for how much content there will be in general, at this point I need to start thinking about cutting back and finishing a minimum amount of content that I could release the game with. The minimum is basically,
20+enemies/traps with h-animations
3 h-events involving npcs
A few other hidden h-animations involving items or props, and some other stuff.
In terms of CGs, that's a minimum of 6. 3 bosses, and at least 3 others. But that's if they're animated.
Anyhow, back to work.