Thanks for playing! Yeah, MZ3D is a plugin I used to make the game and it is browser-optimized but still much less efficient than using Unity or Godot's 3D, so it actually runs much more poorly than expected.
For the Shrine Maidens, you're actually not supposed to take action against them: however, you can bait them to some areas by causing a lot of "commotion", then do nothing there and hope they don't find your head (while searching, they won't go anywhere else).
Also, I may add an option to disable the blur and some other 3D effects in a future update.
Also also, yes, in the Kogasa (exterior) region, if you don't handle the fairies fast enough and they attack Kogasa in that area, some of them are literally impossible to reach: Distract has infinite range, but won't work on attacking fairies, and attack has a range of 12 tiles.
So basically, diligence in that area is important. If not, you have to hope Kogasa can escape to her house on time.
I'm working on a guide of sorts to better explain all of this in the next update, with a few more hints in-game as well!