The thrust the prop provides at a given RPM --whilst the prop is not moving FORWARD, is one thing.
How that changes as it moves and gains speed ,is another.
I have a ignition on two of my new engines (ROTO)-that will read rpm -before takeoff --then after the plane lands, you can again read the maximum rpm achieved in flight. (from an LED readout /memory storage system of the ignition.
This will show how much rpm was gained in flight.
Obviously, if the engine/prop was in a smaller lighter plane - the maximum rpm would change more than if in a heavy draggy plane.
So for a given airframe -and a given engine - the BEST prop for a selected area of performance, could be selected.
Make sense?