I tried 4K using a GTX 960 on ultra but with AA off. It actually runs pretty well and looks decent so I'm curios what others use for settings either in game or NVCP using 4K resolution. All I've done is turn on ambient occlusion with performance option in NVCP so far.

Through DSR ???

You can adjust the smoothness of DSR through your NVCPL to fine-tune the appearance of the DSR image - it's similar to sharpness.

Also there is this wrench icon in your GeForce Experience panel. (after you chosen your resolution, there is a slider to optimize for performance or Quality.)

or

you can just click the GeForce Experience Optimise button.

No DSR, I have 4K set from launcher because I have a 4K TV. I don't use GFE either, I have no interest in the optimization it offers since it doesn't cover all tweaks like ini file changes.