The flow rate can , in theory, be different but not much in this case. The flow from more water in the intake will just be ignored as it is balanced with the output side. If you shut the filter off, it just sits there. The impeller is what controls the flow.
For a more practical way to get the tubing and fittings, I would go to the home center for CPVC pipe. CPVC rather than PVC for the smaller size. Els,tees, and caps are 1/10 the price of tubing and much easier/cheaper to fit together and in place since they are solid. Paint it any color you like. Once designed, the intake can be as simple as slots cut in the pipe with a hacksaw. Join them together and then fit the tubing to it. You can do the same with the outlet if you wish.