While the protagonist is still Mario, the hacks manage to deliver the Touhou look'n'feel (sans the danmaku). Easy to start, but gets ridiculously difficult after a few courses. Also, you need to git gud your platforming skills!
Man, the Super Mario 64 personalization thing is real...
Are these ROM hacks compatible with the PC port of Mario 64 or do I have to nab a N64 emulator?
Nope, those are ROM hacks targeting a vanilla SM64 ROM. Also be aware that most older hacks will only run on Project64, not the newer, better emulators out there, and much less on a real console (via a flashcart).