If you read it all you would see that my point is:
you can't calculate the prop efficiency - you must ultimately TEST in actual flight conditions.
I've absolutely nothing against practical or trial & error tests, it’s obvious that you’ve to check whether the calculation works in practice, but you can in fact get pretty close to the best prop for a given plane if you calculate it in the right way.
But, if you do as your following post suggests:
what I meant is that a high static thrust prop just may provide the best forward speed also -for a given plane - without getting in to formulas (which I detest in explanations ), a very draggy craft may do do best with the best "thrust" prop"
Then you’ll get stuck in the first gear!
Good luck.
[8D]