Found no issue relating to this and as far as I know it's a pretty simple issue to fix. Minecraft (the game itself, not the launcher, that doesn't matter much) runs as an Intel app through Apple's translator on the M1 Macs, and this causes a huge performance hit. Using this launcher script (which doesn't modify the game, just allows it to launch without Apple's emulator) the game launches over 3x slower and has noticeably worse performance, from loading worlds slower to a way lower framerate than when playing the game with the native launcher script.