I don’t have hardware to run 4K, but the changes I did to my settings increased my frame rate so may apply to you…I have a Windows 10 PC with a 1GB GTX 750 and was running at 720 high to suit a TV I use as a screen.
Initially I was getting 60fps on default settings.
By changing these Nvidia video card settings I got to 80fps
i) Set PhysX processor to actual video card not “Autoselect”
ii) Under “Global Settings” turn off Vertical Sync
By Changing these Windows settings I got to 96fps
i) In Control Panel/System/Advanced/Performance/Settings/Visual Effects… Tick the button that says “Adjust for best performance”
ii) In Control Panel/System/Advanced/Performance/Settings/Advanced… Set “Virtual Memory” to “Custom” with minimum and maximum the same size as the “Recommended” size it states for your PC