Not sure if this has been found previously, but with my new game I'm working on, I noticed that:
A) It's butter smooth when in windowed mode and NOT maximized.
B) If I maximize the screen (not real fullscreen but windowed fullscreen) I get nasty micro-stutter quite constantly.
I tried resizing the game-window to about 95% of my screen size (4k monitor and resolution if that matters) and it's still butter smooth. If I maximize the window, BOOOM stutter.
Not sure what that means? I think I'll do some more experimenting tomorrow.