Hey, welcome to Canreef.
For flow through your sump you'll see suggested just the skimmer gph rating to 3x, 5x, 10x etc, but personally don't think there's a magic number but don't need a huge amount. It's okay to rely on the return pump to give flow in the display, though to much, might start pulling back to the display micro bubbles from the drains and skimmer.
For fish only you don't need a large amount of overall flow but if planning corals might want to consider changing you power heads to high flow types.
For a idea of display turn over here's a interesting
thread.