IIRC, VCC is calibrated standard to hit 0 on the VU meter at -18dbfs in your daw. This is a pretty common level for other plugins and outboard gear too, so it's good practice to work around that level anyway. If things sound too quiet that way, just turn up those monitors a bit more. Leave the loudness to the mastering phase.
By the way, you can check how things sound with more or less saturation quickly, without changing the volume. You can do this by going to the calibration menu in VCC, and changing that -18dbfs calibration point to a higher or lower setting for individual groups or the entire session. This way, the lower you set the calibration point, the higher the saturation becomes. Handy for finding the sweetspot on a drumbus/bass, because those usually get a bit more punch and depth by saturating a bit. Too much and it sounds like a cardboard box though.
Once you have found that sweetspot, you can still reset the calibration, and change the track input gain accordingly. This may be the same thing that the drive knob does, I don't know, but I like when the VU meter reflects what is happening to the signal.
