My reason to say think is --- When purchasing a DC, it is designed as the standard 4" type system because the market shows tools with 4" ports. And then a dummy doesn't have to read "Connecting Woodworking Tools To A Dust Collector For Dummys"
My system starts out as a 4" system to the separator can. It leaves the separator can in a 3" line to a short manifold. There it branches to
2-1/2" lines where shop vac hoses connect the manifold to the tools with a 2-1/2" blast gate at the tools. Each of the after thought dust ports are redesigned to work on a 2-1/2" line. I have excellent pickup from everything from the router to the planer and even the TS after a well made dust collection port has been made.
So, think. If a shop vac will pick up the dust after it is made just as fast as it is made, then a shop vac or a DC with a shop vac hose will do the same.
When you go from a small lineal area to a larger one such as that is what happens in your separator can or cyclone, then the suction is decreased and the dust won't flow. The only thing size of the DC will do is overcome this change and make no need to read the above book for dummys.
However, when the dust port is redesigned so that the lineal area of the hose (ie. 3.1416 x 4 = 12.5664 for 4" hose; 3.1416 x 3 = 9.4248 for 3" hose; 3.1416 x 2-1/2 = 7.354 for 2-1/2" hose) is nearly the same as the port. This makes the port move suction like the hose and the chips and dust move in the hose and tool as they were one regardless.
However, it is easier to just buy a bigger DC to compensate for the change made from the hose to the port because most WW'ers don't have the ability to redesign the dust port, so they just hook up a powerful DC to after thought dust ports.
BTW, where were these dust ports on tools 30 or more years old, & why hasn't there been significant change in the DC collection on a TS where DC collection is needed most?