Probably the easiest way to find a decent sp fan is look to see what's on AIO's that isn't spinning at 2000+ rpm. Sp from stats is kinda iffy as there's no standard test unlike cfm. Sp is generally how much water is moved away and kept at bay from the fan. But conditions can change according to angle, water used, container used, distance from fan to container, what part of the radius the fan is set at etc. So everybody ends us with squewed results.
But a fan that performs well on a radiator (there's only a handful of actual rad manufacturers, so they are all very similar) at lower rpm is going to have decent sp/cfm balance through restrictions.
Corsair ML Pro, EK Vardar, Noctua A?x25 etc
Plain fans tend to have better performance than their rgb/argb brothers in the same series.