The mod page does a better job than I could with screenshots/videos. But check it out
It makes Witcher 3 look very cinematic. Looks amazing, more like how it was in E3 instead of what was released. Does take a pretty good PC, mine isn't the best but it plays fine.
Not sure how many still play Witcher 3, but its still fun to me to hop on and play through things...always find many new things and details I missed in the past. The game is so huge.