Try creating a custom resolution in your nvidia settings (1080:1200)
Then edit skyrimprefs.ini file located in my games (C drive) to set that resolution in game (if the launcher would not allow you to pick this one)
1080×1200 is a 1:1 rift resolution so everything looks way better than on 1280×1024 or 1600×1200 resolutions and it works a lot faster.
If aliasing is a problem you can always set some antialiasing (x2,x4,x8) to make it look better.
It should help a lot with fps.
Additionally you can use one of the Z-buffer modes (ok&save + game restart required to take effect)