Eximo :
Only so many different settings to try. Perhaps a clean install of the Nvidia drivers to get everything set back to default, install the latest monitor drivers if you haven't, set your desktop to 144hz or 165hz, turn on G-sync for both Windowed and Full Screen, try both modes in your games. I prefer V-sync on so the GPU doesn't have excess coil whine when it really starts to pump out frames, you can try both. (I have found several games that only work in full screen windowed mode with G-sync, I got subpar performance in full screen mode)
The latest Nvidia drivers have thrown a lot of things out of whack too, though. It may just be the driver itself.
Biggest example I have is that I used to be able to run WoW in Windowed (Fullscreen) mode with no issues, now WoW has some stuttering to it for some reason, forcing me to run in Fullscreen mode, which for whatever reason is lowering my FPS slightly as compared to W(F). In addition, playing video (Netflix or Youtube) in Fullscreen mode (on my secondary monitor), with games in W(F) makes the game completely ignore G-sync and it goes way over the cap, but looks as if it is playing at 30-40fps.
Again, in Fullscreen mode it works completely fine, and in W(F) with video not in fullscreen it runs perfectly fine except for some stuttering at least in WoW (Farcry 5, specifically works fine no video in either mode)
WoW also crashes on startup a lot too, randomly.
Worked perfectly fine in W(F) video or no video before I updated my drivers.
A lot of other people reporting issues with G-sync and new drivers in WoW recently. Could be a similar situation with Payday