> I don't want to have to read a lot of information or setting details ahead of time to be able to run a game as a GM.

That's not something you need to do for OSR, though, at least not in general. Dolmenwood is obviously based on that, it's a complete setting paired with a game system. But you can grab an OSR game system without paying much (if any) attention to the setting it may provide. Hell, even for Dolmenwood, I can't be bothered to read it all (it has a lot) and I enjoy making up my own things, so I'll still use the system and just use the setting as inspiration.

Half of my sessions are, "What monster piqued my curiosity this week on my skim through some system's monster manual? Can I create a scenario around it or a bunch of them?" The other half are "I wonder what the river pirates are up to this week, maybe they raided a nearby town and there's an award out for their capture. But what if they were actually hired to do this raid by someone even more nefarious than them..."

No real setting concerns, drop the PCs in a random place and the players will figure it out.