I'm not trying to be argumentative, but increasing pitch won't necessarily give maximum (or even more) speed, nor will increasing diameter always give more climb ability. Those generalizations are just that -- generalizations -- which are generally true (that's why they are called generalizations ), but often they can be far from the truth.

The pitch/diameter generalization is a reasonable place for SuperAirborne to start, but he is looking for a simple answer to what is arguably the single most complex technical element in model flying. Many (maybe most) modellers have nothing more than a passing understanding of propeller function & its wildly interactive relationships with engine & airframe combinations. That, presumably, is why Jaka is seeking more specific information.

The quickest way to deepen understanding of this topic is through the examination & explanation of specific examples, plus personal experimentation that is based on the knowledge gained from the examples & explanations.