What's preventing you from deinstalling it like any other mod? If you're playing the actual mod (not just the graphics patch), you most likely will not be able to play further with your saves if you remove it.
The D3D11 renderer gets installed by dropping files into the system folder, L'Hiver doesn't (maybe you mean the data folder?). Which one exactly are you talking about? And why don't you just delete the files you added when you installed whatever you're talking about? Make a backup just in case.