When I read @16251's OP, my mind went to a third option... those rare small venue gigs by artists that still draw big. E.g., sometimes big acts will kick off tours with a teaser club date (e.g., Guns n Roses played the Troubadour in L.A. in 2016 to warm up for their reunion tour). And I recall Bob Dylan purposefully played a series of shows in unusually small theaters for him, maybe 10 years ago. And wasn't Prince known to do a "pop up" show every now and again? Sometimes giant bands played club dates under a phony name, etc.
I don't have any stories about seeing gigs like these, and would be interested if others do.