I assume it has some in-built analog-style driveable stuff as it doesn’t clip? So in a sense it doesn’t matter about whether any channels except the master channel go over 0db then?
Also does it matter that my metering is set to +3db digital and yet my projects are set to +6db volume max (which is the minimum value?)
Correct, it doesn’t matter if channels except the master channel clips. There will be no distortion.
The only thing it could affect are certain plugins, which could possibly clip if they are programmed that way.