I run my MIDI tracks at a default volume of 100 (out of 127). So my keyboard always starts out at a volume of 100. In the end a MIDI track could be whatever it needs to be volume wise. The MIDI volume (I'm talking about CC 007 volume) of my MIDI drum tracks hardly ever varies from zero. My MIDI bass track ends up 89-111 and the rest are wherever, typically 40 to 110. Those are all MIDI (CC 007) volumes,
My output tracks on Cubase always start out at 0 db.
My MIDI master volume (CC 136) is always set to 127.
Then I mix the individual audio tracks, which usually end up being about 1/2 way up or a little more. They almost never go above, or even at zero. I aim to record all audio tracks at the volume, or a tad louder than they will be played back. If I'm recording a cymbal alone, for instance, I won't record it loud and then turn it down, I'll record it where I want it, or slightly louder so I can turn it down later, than it wll eventually be. This is important because it affects the tone a lot, even on digital.
Then, and this is the big one, I made a passive volume fader (from a real nice Noble detented fader with a huge knob) that controls the whole volume of everything, so I can control the volume without screwing up everything. That volume goes before my amp and it's numbered so I can always return to the exact volume quickly.
That passive volume control is what cleared up the whole volume mess I was in from about 1983 to 2003. Many of the things that have had the biggest impact on my studio have been ultra cheap homemade problem solvers like my passive control center that houses the volume knob.
For live gigs, too many volume controls can be a real problem. I have cut short lenths of chop sticks and glued them in faders (like on a drum machine) to keep the volume at the full volume. On some dvices, like a SoundCanvas, I have used heat glue to keep the volume knobs at the right place (usually full), and on some gear you can just take the volume knob off and if it's recessed then that takes away one more possible problem.
The whole volume thing took a long time to get even as good as I have it now... it's never really over because the technology keeps changing.