Your question is too open-ended because you are misunderstanding an essential point.

To begin with, we are discussing model applications -- so forget Corsairs, Thunderbolts, Spitfires & any other full-scale applications. As soon as variable pitch & constant speed enters the picture, it no longer fits with model discussions.

As generalizations go, diameter & HP are the most important factors in determining thrust (not speed). The only real reason for going to a multi-blade (3 for example) is that you may not be able deliver all of the available HP with a 2-blade. The performance-based reason that you wouldn't use a 2-blade, is because of diametral limitations. Without diametral constraints, the 2-blade will deliver more thrust for the available HP.

Within the diametral constraints imposed by airframe, ground clearance, or centrifugal force, to transmit more power the aspect ratio of a 2-blade prop will normally be reduced (wider blades) before a jump to multi-blades becomes necessary. At some point, as the blades are forced to get wider in order to transmit the available HP, the efficiency of the 2-blade prop falls sufficiently that the weight & drag penalties of the 3-blade are neutralized, because the 3-blade can utilize an efficient high-aspect ratio shape for the same blade area as the fat 2-blade. Beyond that point, for a given diameter, the 3-blade will have an advantage.

The same constraint also applies to a 3-blade. If you can't increase the diameter, you must make the blades wider. Eventually you will again reach a point where a 4-blade gains an advantage --- and so on.