I'm not very familiar with this, but I know that some action scenes are converted from MMD to Koikatsu. As for modifying actions and camera work, I recall that some creators have done it, though it's quite rare. If we were to calculate the ratio, I'd say less than 1% of people actually modify actions and camera work. Note that when I say "modify," I'm not referring to changing the camera, clothes, or background. I mean modifying the actions, expressions, and transitions to make them look less like those poor-quality HMV-type videos. As for scenes and actions, pure dance animations can likely be found online. As for sexual actions and such, because they're usually manually made, they often aren't shared publicly. However, some creators do sell these animations. For models, you'll either have to search for them yourself or pay to have them custom-made. You can check the forums on IWARA for discussions. Basically, Koikatsu/VAM/HS2 are programs with very low ceilings and even lower floors. As long as your computer can run it and you can find the resources online, you can create content. For MMD/Blender, the floor is very low (if you're just applying dance animations), but the ceiling is very high. You only need to take a look at the most-viewed videos on IWARA to understand that.
