Volumetric Lighting and Contact Hardening Shadows are hard to notice on Ultra unless you compare two screenshots side by side and look for the differences. Save yourself the trouble and leave them to On or Off depending on how much of an fps boost you want.
Do the above and watch your FPS jump. I'm currently getting 50 fps average ( using the provided benchmark ) with a 980ti @ 1440p on Ultra with MSAA Off and Volumetric Lighting + Contact Hardening Shadows set to On.
EDIT: Updated review to mention Contact Hardening Shadows as well.