Should we keep vsync disable?
That is a good question.
When testing your FPS it should be turned off so you can see the actual FPS you are getting. I use the STEAM overlay for FPS.
Vertical sync was needed in the old days so you didnt see tearing (weird artifacts) on the screen as you drew new data to the frame buffer and it was showing old data. So you would get half new data half old data.
V sync makes the GPU wait until an old CRT monitor is in the process of moving the electron beam from the bottom of the screen to the top. So no data is being drawn while you put the new image into the buffer. Early videocards only had memory you could write to while it was not being read from. So Vsync was the only option. LCDs do not have a refresh exactly so it may not be needed in most situations. And all it is doing is adding a WAIT period for each frame you draw and slowing down your game.
I always have it on since I only play Coh2 and 60 fps is fine for me. When I turn V sync off I get much better fps but then my GPU fan starts spinning up and making a lot of heat.
You should definetely turn it off and check how it goes. Also verify that the graphics settings are at a high refresh rate. When I start changing resolutions from 1080 to 4k, windows changes my refresh rate to 30 Hertz and I have to manually fix it. I am only using HDMI cables so I dont think it can do 60Hz at 4K. I think you need a DisplayPort cable for 60Hz. But I am guessing.
SUMMARY
For BEST performance, turn V Sync off and if the screen starts having distortions that bother you, turn it back on.