norbique

We must clearify something here.
It's not the prop size/pitch that's the first thing to make a boat faster, but power is.
Power = Voltage * Current

So to go back to the debate of HV and LV setup heres a little maths (this is theory, I don't bother with motor/esc efficiency, power loss due to friction etc.):

Let's suppose we need 2kW of power to push our hull decently. Lets see how much current would such a setup require:

Power = Voltage * Current -> Current = Power / Voltage

LV setup: 6S pack Current = 2000W / 22.2V = 90A
HV setup: 12S pack Current = 2000W / 44.4V = 45A

This shows clearly how things are related. The HV setup would run less amps for the exact same amount of watts in. And the less the current, the less the heat loss which also means higher efficiency.
We can also see since the HV setup needs lower current from our packs for the same amount of motor power, the packs will hold their voltage higher, this will also result in a faster running boat. We can generally say the less the current the better off we are. Unfortunately, the HV ESCs are more expensive than the LV ones mostly because of the higher voltage MosFET transistors used in them. this is the only reason I stuck with the LV setup.