If you have a 3070 right up to a 4090 and have REBAR enabled in BIOS and your GPU, it might be worth forcing rebar through Nvidia inspector for The Witcher 3. I gained around 5fps+ across the board, where it was dropping to 45 it's now above 50-55 in the same areas I tested.. Sure the game still sucks for performance but every little helps right?

Load the latest Nvidia Inspector : https://github.com/Orbmu2k/nvidiaProfileInspector/releases
Rebar is now located under '5- Common' and the three options are labelled 'rBAR - Feature, Options and Size Limit'
Select your TheWitcher 3 profile at top left, then make sure rBAR is enabled, and click APPLY

Close Nvidia Inspector and give it a go!


(For those who don't know what RBAR is and how to make sure it's actually enabled on your GPU in the first place, google it, it's a bit long winded)