On my 125 i was close to 500, on my 120 now I am closer to 300.
IMO it is more about the sump volume to determine. I have a much smaller sump on my 120 then I had on my 125.
You want the water in the sump to spend some time with the filtration. Let the filtration do it's job for awhile and then return the clean water. 3-5x the tank volume through the sump is perfect I find. But you also want the water in the sump to move a bit as well so for me that is kind of the sweet spot.
I could easily do more flow through my 120g now, my pump is adjustable and I have it set at 20%. Turning it up is just a button. But I find at 20% I get better operation out of my protein skimmer.
On my 120g I have 2 one inch drains and they can handle up to about 1200gph, so I have more then enough. No harm in going bigger, but IME it is really not necessary. IME the noise comes when pushing to much water through a drain as the added water in the pipe closes the air column and leaves that suction sound. Having two little coming through is not a problem.
All this said, I do not have a low flow tank. I have 2 WP40's and an Rw 15 in the tank for water movement and my returns have penductors on them. I alternate when each pump is on and off through the day and my return is through a SCWD.
SO I like a lot of water flow, more then most. BUT not from the return.