The current version of RPCS3 can run Nier at full speed (30fps or 60fps with right FPS during cutscenes if you use this patch https://wiki.rpcs3.net/index.php?title=Help:Game_Patches#NieR). Previously I tested Nier Replicant but the fantranslation out there is not faithful to the Japanese script therefore from now on I will only test the official release. A remake of Nier Replicant for PS4, PC and Xbox One has been announced anyway.
As you can see lots of progress has been made in the compatibility of the emulator with this game. At the moment the emulation is rock-solid with minor glitches (shadows on the characters, pixelated bloom effect if upscaled). I do not know if the developers will fix these minor problems in the next releases of the emulator.
At this time, Geek Sentai has 11,005 views for Nier spread across 7 videos. About 3 hours worth of Nier videos were uploaded to his channel, making up less than 0.21% of the total overall content on Geek Sentai's YouTube channel.