Concur with the hot tub capacity enforcing with ~1200 pax on Magic 11/27, there's a labeled queue on the port side of the Goofy pool for the family ones (the queue for the Goofy pool itself is on the starboard side of it). Basically people stand there watching the Funnel Vision movie until it's there turn then hop in. Lifeguard generally manning both queues, sometimes two lifeguards splitting the duties, seemed to time the cycling with the jets turning off at least some of the time. Most of the time the line was empty. Also don't think I ever saw anyone waiting for the adult only hot tubs at all (or even a queue for that matter), but as you know those don't have lifeguards present to enforce anything so people were likely intermingling.