Some games won't run in "exclusive" fullscreen.

I have this issue that some if not most games run in boderless windowed even when the game is set to fullscreen.
Alt+Enter doesn't work either.

This causes some games to run poorly, like CSGO wich fps keeps fluctuating between 50-60-70-100+fps.
No matter what settings i use, so i think it's cause it runs in borderless window.

I'm using latest NVIDIA drivers and Windows 10 Home 64bit, specs are in my signature.

 

Are you using a 60hz or a 120hz monitor?
If you're using a 120hz monitor, see if 60hz (which is expected to always be available) is missing in the EDID. If it's missing, add it back in ToastyX CRU.

 

Has nothing to do with borderless windowed. I used to play CS in borderless all the time and a single 780M not even being stressed got me 200+fps at max settings. Your 670MX is weaker but not 50-100fps weaker. Something else is the issue on your system. Since you're on W10 home, the problem is likely the fullscreen optimisation crap in the creator's crapdate which you've been forced to have because I have no idea why you are using W10 home.

Right click csgo's .exe and go to properties, then under the compatibility tab check the "disable fullscreen optimisation" box and then reboot your PC (because CS is crap and a PC reboot often helps it perform better for literally no reason I could ever find, ever) and see if you don't get a solid 200fps.

 

I only have a windows 10 license of the home version, i didn't even know the update braught this with it.
I'll try your suggestions, in the meantime i got rid of the fps drops,if shader quality is set to high instead of very high i get 100-130fps with 2x MSAA enabled.

 

Go to Windows Settings -> Gaming -> Disable "show game bar over fullscreen games Microsoft has verified"

And reboot

 

The only game I've encountered with this is Dawn of War 3, but checking the .ini and/or launch options should resolve most games not running in exclusive fullscreen.