We couldn't fast-travel to Velen at all with Super Turbo Lightning Mod enabled, even though this mod is compatible with the update according to CD Projekt Red. , it does seem that some of them still don't work and can cause performance issues. While CD Projekt Red have released a list of supported mods for the next-gen update Go to Options, Video, Display and there you'll find the 'Maximum Frames Per Second option.' Some players report that removing the FPS limit can improve the performance so set the FPS limit slider to 'Unlimited'. Remove the FPS limit in the in-game Video settings Go to Options, Video, Display and under Display Mode choose Full Screen. Setting the game to Full Screen has been proven to help increase performance before in The Witcher 3. The Witcher 3 sets the display mode to Borderless Window by Default.
If you play on Steam, right-click The Witcher 3 in your library, go to Properties, General tab and add '-dx11' (without quotation marks) in Launch Options.