Am able to run at a rock-solid 60fps at 4K finally (with tuned settings mostly related to terrain rendering (object/grass/tree distance), but textures at full w/reflections, SSAO, etc), and it looks glorious. Amazingly, if I bring it down to 1440p, it GSyncs right up at a smooth 120fps.
Using an overclocked 2080 Seahawk X (non-super) for those wondering; runs average 94% usage in-game @ 4K, 82% or so in 1440p.