This game doesn't support Gsync out the gate and it doesn't have exclusive fullscreen.
I also found that while the game runs at high FPS, it stutters above 60FPS because the camera updates scale properly only up to 60FPS, so past that, even though frame-times are completely fine, the game itself stutters.
To fix stutter, using SpecialK test branch, you can force exclusive fullscreen, 60FPS cap and 60Hz refresh rate. I wrote a steam guide too https://steamcommunity.com/sharedfiles/filedetails/?id=2155384839