The alleged performance penalty for borderless window versus full screen was removed from Windows about two years ago so I wouldn't worry about it.
That said, I am using borderless just fine on an nVidia 1060 so something's up with your presumably much newer card. What resolution are you trying to hit? I guess the game's native logic might just fundamentally not understand ultrawide if you have that?
That said, I am using borderless just fine on an nVidia 1060 so something's up with your presumably much newer card. What resolution are you trying to hit? I guess the game's native logic might just fundamentally not understand ultrawide if you have that?