twoD

I've run B2 in Stars Without Number basically out of the book other than all of the monsters being replaced by giant insects and treasure appropriately converted. There is no real reason why you can't use traditional keyed maps for sci-fi in my experience.

I wouldn't really call it dogma. I think the OSR has far more diverse interpretations on how to play a game than most RPGs.

OSR games generally offer a great chassis for dungeon and wilderness exploration with fast, high-stakes combat and are compatible with many high quality modules.

3d6 down the line was the standard method for the White Box, B/X, and AD&D 2e. AD&D 1e was the outlier of the TSR systems in this respect so it makes sense that many people in the OSR tend towards 3d6.