Here’s my last answer to the question of “what Quake maps to try”, from a couple years ago.
Tulpa also linked this once which still seems like a solid recommendation.
100+maps considered aces but the list is over a decade old now so no doubt it’s missing newer quality stuff that’s come out since then.
I’ll also recommend checking out Warpspasm if you like bigger maps. The whole schtick there is the maps are stupidly huge and have hundreds of monsters. It’s honestly overkill but some have some neat architecture.