The answer is not that simple, there are mulitple parameters used by the people who seemingly effortlessly play piano on guitar:
- keep polyphony at max 3-4 voices at a time, use a sustain pedal for the bigger voicings.
- don’t listen to your dry guitar, play softly so as to forget your actual fingerplucks.
- set the noise gate to a level where you have a connected feel between fingerpluck action and pianosound. Doing this will help you forget the physical pluck, and learn you to play on the virtual pluck.
- Velocity is a bit tricky: the curve knob can adjust this a bit.
- For more and harder control than the buildin noise gate and curve, there is a midimachine here on the forum. It also has a retrigger filter. See Custom_Gate: A hard midi startgate and retrigger blocker
- Others have used a compressor in front of MG to make pianoplaying more smooth, I didnt test this my self.