I saw in the rules the RetroArch is banned as an emulator, but RetroArch is a frontend that can use other emulators like SNEX9X. Is using SNES9X as the emulator under the RetroArch GUI also banned? I couldn't find anything to clarify this point.

This is the method I use to do Alohomora locks fast and consistently on any difficulty, without glitches.

It seems it's possible to buffer basic casts. An easy way to try it out is using the training dummy in the Crossed Wands area. When you get to 4 basic casts in a row, just tap your basic cast key 4x inside of about 1 second, and you'll automatically fire off all 4 casts in succession.

This appears to work just like any standard buffering, queueing them for the first available frame. Not a big time save, but added up over a run, it can be, especially if you factor in the extra 1-1.5 seconds you have to read the battlefield or react while the queue is dumping.

It also means a bit less fatigue knowing it may be completely pointless to just spam the key to try to press as early as possible after a cast finishes.