I've heard tales of Ritchie Hawtin playing multiple turntables (6-8 depending on who's telling) where he'd have tracks separated as stems into dub plates and do live remixes by swapping out the plates. The things people did before Ableton!
I saw him do 3... maybe 4? tables? But mostly 2 or 3 decks plus a 909.
Around here in Toronto area we had a local (Jeff Milligan / "Algorithm") who was famous for absolutely precise beatmatching, and often 4 deck mixing. Very minimal wonky/bleepy techno.