Yes, you can hard-wire the control panel. The piece you should look for to anchor it is called a strain relief cord grip.
From a 50a circuit breaker you should run 6awg wire to the control panel. Wire is sized based upon the circuit protection (breaker or fuse), and smaller than 6awg the wire could catch fire before the breaker flips. If you are putting 25-30 amp breakers in the control panel, you can move down to 10awg wire after those breakers. Similarly, if you use other breakers/fuses downstream, wire from them can be downsized accordingly.