You would always prefer bypass over
oil starvation so go with lower bypass, most are 9-11psig. Good thing about FL-1A style filters is they are clean side bypass, most are dirty. I have never seen anything over 3psig differential across mine, I had some gauges before and after and did extensive testing. Royal purple has syntheic media, wire mesh maintaining pleat spacing etc. they actuall sent their filtration charts to me including flowrate vs pressure drop. at 8 gpm they are like 3 psig at 212F 10W30. I thing motorcraft FL-1A was 6 psig.