Pitch, diameter, blade shape and number of blades determines load on the engine... and how much thrust you are attempting to transfer to the water at any given rpm/
Too much diameter and pitch for the blade shape and count will overload the engine and make you SLOWER. plus burn up the engine.
An outboard typically comes with a compromise prop that will be OK for general purpose but may not be best for your hull. Generally a little less load than the engine can handle, so you have to watch rpm at top end to prevent overspeeding the engine (which throws rods).
Many people never change from the OEM prop and are happy. Someone looking for max performance will do some testing and find the best prop for the way they want to run the boat. Skiers want more power, racers want more speed.