Indeed, you can use any receiver you like so long as it accepts the standard JR wiring to plug the servo/ESCs into.

The Devo 7e has more channels for a start (6 I think) and is much more programmable than the T6A I believe. I use a OrangeTX transmitter that works nicely for my purposes.

I believe the difference between braked and unbraked is that when you go from 100% to 0% (for example), the braked ESCs will slow the motor down quite vigorously to make it stop quicker. ( ).

The servo linked looks OK, it is the torque reading that will tell you how powerful it is, which is important for a flipper. However, for an axe, speed is more important.