Recently I formatted my computer and installed Windows 10 in it, in the first days it went so good, I think that's because I installed an old version of W10, 18th April exactly, and I didn't had any problem but days ago the pc got updated to a new version. I don't know what's new in that version but I've seen like a "Game mode" that improves the game performance to a "better experience".
I don't really know if it could be the cause of that but I haven't seen anything more than this. The thing is that when I open the game and start playing everything goes OK and I can play with the normal FPS, like 300-400, but when I exit the fullscreen mode and go back to it, I start feeling less smooth in the game. I don't know how to explain it but it's like the FPS doesn't go down and moving the mouse becomes something annoying.
I have to say that when I activate the VSync the problem solves but I don't like playing like that because it feels rare to me. I hope you could help me, that's very uncomfortable.