My pump is coincidentally almost exactly half the capacity of yours; it's rated at 40 l/m and, again coincidentally, I cobbled together a 24-outlet manifold. I used 3/4-inch PVC and got some threaded brass valves that simply screwed into pre-drilled holes in the PVC; put a dab of silicone on the threads before tightening. This thing goes together in less time than it takes to tell, and it has worked flawlessly. A single standard airline runs from each valve to the various bubbly-air-things I have, again all homemade.
Some of these individual airlines are only a few feet long; others run more like 30 feet; and two are almost 60 feet long! At the moment I have a total of 18 running, but they're always being added, changed, removed, etc. Depths are almost all between 18 and 23 inches. Still lots of air being exhausted through a couple of valves that are just bleeders. I have each valve numbered and keep a written chart showing which valve feeds which tank; in my fishroom, with some tanks here, and a couple more over there, and one down there, and two upstairs...not keeping track of them will lead to madness.
Limits on air through a small diameter air line? Of course there must be limits, but I have no idea what they are, or how the various configurations you mentioned would compare. I divide everything into one of two categories: enough air...and not enough air. I don't trust the rated capacities of air pumps any more than I do the rated fuel consumption of different vehicles or the tank-size capacity of various filters. There are just too many variables for those ratings to be anything more than a very rough comparative guideline. I know my buddy's Alita pump had similar numbers to mine, but for whatever reason it seems much less "powerful", for lack of a better term, than my HiBlow.
Don't forget also that the capacity of an air pump is determined not only by the volume of air it produces, but also by the pressure it creates. I seem to recall that mine is somewhere around 90 watts, so maybe it generates more pressure? I never got into the details of that...remember the enough/not-enough thing? I have enough, so...that's enough for me.
But you might enjoy playing around with those numbers as well.