On smaller electric planes, switches don't provide any value. Extra weight, cost and just one more part that can fail.
The flight battery needs to be swapped between every flight anyway so save the weight and simply use that as the switch. The other problem is that many small switches are unreliable and easy to damage. A bad switch can cause your control system to turn off mid-flight.
As to your specific idea to put a switch between the ESC and receiver this is not a good idea because it will NOT cut the power to the ESC and by extension the motor but instead only cut power to the receiver. The ESC will go into failsafe mode and if it is set correctly, the throttle will go to zero, but if set incorrectly the motor could spin up. In any case the ESC will still be pulling some power from the battery and will discharge it to zero and ruin the battery if left plugged in over night.
If you must have a switch it should to be between the battery and the ESC so that the power is completely turned off when the switch is open.