I’ve got 2 on my 40 gallon, and have them both at maybe 30%. It’s nice that way because they are very quiet at that level. At 100% they aren’t loud, but they are audible. As I add coral, this allows me to up the flow easily as needed. It also helps me avoid having dead spots with the two pointed different directions (I’ve got on in back and low, the other higher towards the front on the other side.)
I have two MP10s on an IM nuvo 20. Just dial them up or down as needed. I've never been able to get decent flow with a single powerhead unless it a very small tank like my 8g.