Whatever prop you choose, I think you will find it difficult to reach your speed limit of 120kts in level flight.
I used to have a fixed pitch prop on my 912ULS-powered Pioneer 300 and happily cruised at 120Kt.
I then changed to an Idrovario Medium prop - the fuel burn at a 120kt cruise hasn't changed despite a lower rpm (though I can now cruise at 135kts if required albeit at a higher fuel burn), but the takeoff/climb performance is hugely improved.
The engine/prop combination worked very well when operating hot & high in Morocco, Spain etc. It should suit Ecuador.