I think the ram will help Scorpio run the games more like the PC version. Witcher 3 on regular xbox and ps4 use 5gbs so if the pc requres 7gbs the scorpio version will probably have similar performance to the pc version. Thats just my theory.
Performance has nothing to do with VRAM. They are 30 fps on both consoles cause CPU and GPU were too weak for more.
But if Witcher 3 was to receive Scorpio patch it could employ Ultra details in 4K and probably still 30 fps cap.
Witcher 3 on consoles runs on medium settings, but textures and water are set to high. 900p on Xbox One and 1080p on PS4.
It's actually one of the best optimized games on PC, but console version is pretty good too.
Just under 2 GB VRAM usage on Ultra details and that's with Ultra textures as well. They barely look any better than High textures on PC and on consoles though. Still looks great for 2015 open world RPG, and 4K Ultra would definitely improve the experience, even in 30 fps.