You always want to keep the engine in the right RPM's for the best power. Go over the power curve and loose power, but too much prop on and the same result.
If for example your engine calls for a 12x8 the you can use a 14x6, 16x4, for 3-D. Now if you want speed you can 11x9, 10x10. As you can see for every inch in dia. lose or add a inch in pitch. This will keep the RPM's at the same level. Dennis