It depends on the Guitar for me. The Les Paul is medium low, no buzzing AT ALL, plays like butter. The RG550 I like real low, I like it when it buzzes, like, I'll just attack the thing, and all you hear is pure scratching, sounds amazing. But the Strats I like it medium ... and I play them hard.
As for Bass, I dunno, I hate my bro's bass 'cause I REALLY can't slap, it just doesn't ring. I'm not a bassist, so I don't know anything about it, but I know that I have tried other basses that I was able to slap nicely.