When The Witcher 3 launched for the original Xbox One back in 2015, it only ran at 900p (1600 x 900) resolution and had trouble maintaining a stable 30 frames per second. The same unpatched version of the game, running fresh from the disc, hits 60 frames per second more often than not on the Xbox One X.
While subsequent patches upped the resolution to 1080p and locked the game at around 30 FPS, The Witcher 3: Wild Hunt launched on the Xbox One with its framerate unlocked, which makes an excellent candidate for demonstrating the additional power available in the new Xbox One X. NX Gamer, who's been following the game's Xbox One framerates since launch, created a video demonstrating how the faster hardware affected the unpatched game. It's pretty impressive.
Mind you, this trick only works on the disc version, before any of the game's numerous updates are applied. And while a good amount of the game runs at 60 frames per second, crowded cities knock it down into the 40s.
Unfortunately, I own the digital version of the game, which automatically downloads patches when installed, so my copy of The Witcher 3 maintains its locked 30 frames per second on the Xbox One X.
There is an official Xbox One X update coming for The Witcher 3, which will allow the game to run at 4K resolution while adding ambient occlusion, texture filtering and higher resolution textures overall. While it's likely the 30 FPS lock will remain in place at 4K, there seems to be plenty of power available if CD Projekt Red wanted to toss in a faster, lower resolution mode.