KV means, revolution per volt, so if you increase the voltage to motor, the prop will spin faster.
Lets say, if you use a 6s Lipo and a motor like Tiger MT2826 / 550, you can use even 11" props to lift a craft AUW 5 kg, with a flat hexa setup.
But, if you use a 4s Lipo, you'll have to put at...