Quick (or maybe not) discussion on the amount of thrust that a prop generates:

Three main things affect thrust, in no particular order: rpm, diameter, pitch.

Given the same rpm, increasing the pitch or diameter will increase thrust. However, increasing diameter has a far bigger effect proportionally than pitch. Hence the generally addage about going up in diameter, but down in pitch to generate more thrust. Basically what you gain from the diameter is more than what you lose from the pitch.

The other issue is whether just increasing the diameter or pitch will increase thrust, given that this will reduce rpm. Well again in most cases, diameter gains will generally outweigh rpm losses, but pitch gains is a close run thing, depending on whether you are improving the efficiency of the engine or not, ie whether losing rpm means you are increasing or decreasing torque.

Another thing to consider is dynamic v static thrust, and this is where pitch is important (dynamic thrust is where the propellor is already moving through air). Big dia/low pitch props generate lots of static thrust, but less dynamic thrust. Thats fine for slow flying funflys, but not much good for fast flying pattern ships.

Finally there is accelleration v speed. low pitch props generate give great accelleration, but obviously far less speed, while high pitch props arn't good at acceleration, but do give speed. A bit like low and high gears on a car or push bike.

Other things to consider are:
efficiency of the prop design (eg stiff APC passes on more power to the air, and absorbs less in flexing),
chord of the blade (wide blade props creat more thrust than narrow),
number of blades (2 blades are more efficient than 3 etc).

Ultimately if you want to make a big difference to thrust, you need a bigger engine as I said. Changing props is generally just fine tuning.