Any 12v dc power supply with sufficient amperage will work fine as a source.

Amperage is based on resistance and voltage with I=E/R (I is current, E is voltage and R is resistance.) so the lower the resistance the higher the. Current will be relative to the voltage. With a low enough resistance you can get 100 amps at 1v.

The rating on the esc is based on how much current can pass through it safely. The total current draw would be based on the motor as it is the true load in the circuit.