For those running 4K with a single Titan X, SLI GTX970s , CFX 290/290X, SLI Titans OG/Black or SLI GTX980/GTX780Ti these seem to be the best performance/IQ settings I have found for a solid 60 FPS with vsync off in-game but set in the NV control panel.
FXAA ON
MSAA OFF
Population Density,Variety and Distance Scaling - 50%
Texture Quality - Very High
Shader Quality - Very High
Shadow Quality - Very High
Reflection Quality - Ultra
Reflection MSAA - X2
Water Quality - Very High
Particle Quality - Very High
Grass Quality - Normal
Soft Shadows - Softest
Post FX - Normal
AF - x16
Ambient Occlusion - Normal
Tesselation - Normal
Advanced Settings are all off.
These provides 60 FPS across the different areas (dips are only down to 58ish FPS) with a Titan X @ 1377Mhz on the core (no mem OC).
Depending on your setup you should be able to add some draw distance. I personally prefer not to have dips.
Total VRAM indication in the menu is 3026MB so I have added the GTX780Tis to the mix of setups for 4K.