We may need to be careful here.
I know nothing about a Katana (other than it is a composite 2-seater) but my son has one on FS2004 and the prop pitch control turns the blades around when sitting on the ground! This suggests that either it's a duff FS2004 model, or the prop is not the standard constant-speed prop.
Assuming a standard CS prop however, this subject is massively over-cooked. You climb at max RPM to top of climb, then set RPM back to cruise RPM and leave it there until short final when it goes back to the "max" lever position. For high altitude operation, say above 10,000ft, one goes back to max RPM, to give the engine as much "suck" as possible. That's it!
Some engines have operating limits e.g. the IO-540-C4 should not have MP above 23" if the RPM is below 2300, but above 2300 one can have any MP. Or something like that; I have the chart somewhere.