What is the difference between a 30 amp esc or a 20 amp esc. Is it the input or the output that is different?
Both. A 30 amp ESC can drive a load up to 30 amps, but it still needs a battery that can deliver that much in order to do so.
so if i were to only give a certain amount of current to a 30 amp esc would it work like a 20 amp one?
Yes, I think so.