To me that question is a paradox.  Turn up the master then you must turn down the channel and the guitar volume.......  You're back to square one.

The signal flow is guitar, DSP, V1, then the Power tubes.  Turn up one then you must turn down the others to get the same output.

A high guitar volume drives the front end of the amp harder (the DSP/etc) and makes it drive everything else behind it harder, but it's as loud as hell then and that doesn't work in the end.

A low guitar volume means you need to crank the channel volume up to maintain the output, if you leave the master as it is.

Turn up the master then turn everything else down.  You're back to square one again.

I like a pretty low guitar volume because then I can turn up the channel and drive V1 hard, which in turn drives everything else harder behind it.  Then I can crank a little more on the master.

Just cranking the master doesn't do anything for me, never did.  I must start at the sourse, at the guitar,  and work my way through the amp.  Then it makes sense to me, and it also sounds better to me that way. (IMO)

BTW:  If you're interested in just cranking the master then you need to watch that vid that was recently posted.   After watching it my words might not seem so strange after all.

Good luck man

M^T