In-ground cleaning system, pump motor replacement question

Hi all, I've got an in-ground pool cleaning system that used to work when I moved in to the house a few years back. I had an issue with my primary pump motor and had it replaced and ever since they system doesn't seem to work quite right. I noticed that when both pumps are running it seems to starve the in-ground system and I believe my primary pump motor is a stronger (more HP) motor. I'm wondering if anyone has any knowledge of if the two motors should be identical (they were originally, before I replaced one) or if a slight variance is acceptable. The in-ground cleaning pump motor has since failed so I need to replace it anyhow.

Also, can someone please confirm that it is a best practice to have both pump running simultaneously or should just one or the other be on at any given time? My only other thought is if the plumbing may be causing the problem. I can share some pictures if folks feel that would be helpful but hoping that this is a common issue from mismatched motors.

Thanks!