Nier: Automata is one of my most anticipated games of the year, but when it launched last week it did so with a host of performance issues. Typically enough, the community is on the case: Steam user Kaldaien has created a fix which reportedly improves framerates, as well as quashing a bug which prevents the game from rendering at the user's native resolution.
I haven't tested the fix (I don't own the game yet), but many reddit and Steam users are reporting vast improvements on framerate – the improvements include a new limiter, which you'll want to set to 0.00.
The full notes are over here for the fix. Keep in mind that there are two versions of the installer and, crucially, I haven't tested this myself so do so at your own risk.