regarding fixed prop: 2,400 RPM @ best power = 65% power; 2,400 RPM @ best economy = < 65% power
Not quite. If at a particular altitude 2,400 RPM equates to 65% power it matters not if you are operating at best economy or best power mixture. To produce a given RPM on a fixed pitch prop at a given altitude takes a given horse power. Whether that horse power is produced at a best power or economy power setting is inmaterial. The TIO-540 at 65% power and 2,400 RPM burns 16 US gallons per hour at best economy and 19 gallons per hour at best power.