With MG2, there are 3 modes:
piano sustain – like a piano pedal
hold instrument – current notes on hold, switch to guitar. no further midi is send
forward cc64 to instrument – the standard pianopedal is send to the synth
The one I mentioned before (2 in MG2) is the hold type 2 in the GR55.
Regarding the audio interface, everyone will find this or that system more convenient and better suited to them.
Personally, I don’t recommend an audio card integrated in a controller, firstly because it is less scalable: if you want to change the controller, you also have to change the card, and secondly because if it breaks down, everything breaks down.
Finally, while the controller remains an accessory that can change according to the context and the evolution of the equipment, an audio interface is the heart of an audio equipment: it is the one that prevails in the choice of its characteristics according to the requirements that one has, it is the central element that can be used for years without needing to replace it (I speak for quality equipment).
The main qualities of an audio interface are its reliability and especially its stability, hence my mistrust of “all-in-one” devices. I use a proven RME Babyface Pro that I can rely on.
Latency is a problem that comes afterwards. All quality audio interfaces handle latency very well.
I use in live simultaneously several instances of my plugin host, including 2, sometimes 3 virtual amps (S-GEAR and Nembrini BG Extasy) in parallel, more than ten effects and processing plugins, several virtual synths, audio and midi players for background ambiences or synth loops, 1 or 2 loopers . I don’t encounter any latency problems or audio artifacts.
Of course, this is only of interest and value if all the hardware and software equipment are also configured and optimized for increased performance, giving priority to stability, hence the need to dedicate a computer solely to audio applications by removing unnecessary programs and functions and configuring all services, sub-services, routines, extensions, etc. to ensure maximum stability. This is the only way to be able to play on stage with complete peace of mind and to devote yourself solely to your art.
And MG2 is a very stable software that deserves to be used in a stable environment.