RE: Prop Selection and battery life
Power is watts. Changing propeller sizes, pitch, and RPM can increase or decrease efficiency.
The task you have requires a certain amount of power.
Within reason, you can play with props, current and voltage limits using ECalc/prop calc.
The motor you are using with a 6s battery should turn ~9000 RPM at full throttle with the correct prop,
assuming 4v per cell. The current should be about the maximum rating for the motor for maximum power out.
Prop pitches above 8-10 tend to be less efficient. A larger prop with a smaller pitch
is usually preferred to a smaller prop with a high pitch.