As for the multi-motor setup, you will need an ESC for each motor. But since all your motors are all doing the same thing, you can split your Rx throttle port to all the different ESC's. Or you can run two Rx's with two motors on each Rx, or one Rx per motor.
You'll want to run a separate BEC for your Rx if running one, just to make sure you have good power for your Rx, as you can get some signal degradation splitting the signal 4-ways. Not signal from the Tx to the Rx. I am referring to the PWMNsignal going from the Rx to the ESC's. This does require good power for your Rx to push the signals out cleanly. A 10A BEC will probably be overkill, but it'sgoing to be cleaner power than your ESC will provide.
Calibrating: Make sure you calibrate all 4 Esc's at the same time. You don't need anything special in a radio for this if sticking to one Rx. It is not any different than running one ESC/motor if running a single Rx. If you do end up using servos elsewhere. I would probably add in a separate Rx for those, especially if running one Rx to feed 4 motors.
In the MT12 you setup multiple Rx's by pairing all your Rx's in the same model in the setup screen. You would simply give each Rx a separate ID. I would also label each Rx with the ID you assign it in the radio, as it makes things easier later.
The best way though would be to use a flight controller. This would get your motors a lit closer in sync.
