The activity factor is the ratio of the collective area of the propeller blades to the area of the propeller disc.
I cruise the Teal 24" 2100RPM, and is seems very happy. I can't say that that is an authoritative power setting, but my plane is non certified. I have done detonation testing of an engine with the same compression ratio, and the data from that testing makes me comfortable with this power setting. I do have an engine scanner so I can watch temps very carefully.
Wood blades do tend to be more quiet, as they lack the twang of the metal blades.