Aquarium heaters are probably more efficient than heating from underneath with pads. You could use one digital temp controller in one tote to heat all the heaters in all the seperate totes, as long as the water levels are roughly the same. Same with the heat pads, as i'm sure you guys would know.
I think the only real practical upgrade would be putting a cycle timer on the pumps, so you can tune it to get the optimal air/water ratio's. For example: 37 seconds ON, and 3 minutes and 39 seconds OFF, etc.. The schedule would change as they develop, for maximum control.
24/7 spray will get you roots, either way.
DWC cloners work just as good, if not better than LP aero cloners. With enough aeration, the bubbles popping at the surface create a mist with finer particles than an actual high pressure aero nozzle can produce. Coating the stems with mist and bubbles, instead of pelting it with aerated water droplets. Find the "zone" when you get the water level height just below all the cuttings that are at the same height too.
I dunno though, they both work great. The only difference I ever noticed was none. It was mostly up to the cuttings themselves when they wanted to root, or different environments.