As John mentioned, you should start with the midi implementation of each gear in terms of what can be controlled from an external MIDI device. The Korg NanoKontrol2 you mentioned is really for working with DAWs or a software arranger like vArranger. If you just want to control volume and reverb, you could use something like ControlFreak by Kenton if you can find a used one. The Korg MicroArranger has a very good MIDI implementation; many of its functions can be controlled by standard MIDI messages.