It's weird undocumented the compiled Quake BSP format is. The best, most definitive document I can find says "lmao this might be wrong because pre-release shareware version". It's probably correct, but it's shocking how no one had definitively documented the format let alone the new formats. You have to reverse engineer it from existing code.

I also can't figure out what the main feature support difference between Quake 1 and Quake 2 is. Anyways I'm pretty sure BSP is the correct choice for level stuff, and if I can leverage editors like Trenchbroom that'd be great.

I dunno, is BSP too old fashion? Probably not for a CPU rendered game.