I was able to run Nier: Automata at 1440p60 for the whole game.
I did not observe any real framerate dips, that I can remember.
I had 8xMSAA turned on and texture filtering maxed out.
The game was impossible to run at 4k, even without any anti-aliasing; I use a 1080Ti.
The PS4 version only runs at 900p with little to no AA, and the PS4 Pro runs at 1080p with moderate AA.
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As for the mouse glitch, I only suffered from it, if I used my KVM switch.