it also seems like that would not be able to protect you from overs then, you have to make sure you aren't clipping while the fine adjust is at 0, cause if you are, then lowering it would just cause flat wavs that are lower than 0 dbfs, like bricking does.
Fortunately the preamps have their own clip indicator to the left of each meter. If you reduce the level of the inner knob below the "noon" position in order to avoid the digital clip indicator to the right of each meter being triggered, then almost by definition the preamp will be clipping anyway. If you turn it above the "noon" position, and you don't trigger the digital clip indicator, you can be sure that the preamp will not be clipping. If you turn it up to the limit, you are adding 8dB of gain, and if the meter is still not getting near full scale, then you might as well turn up the preamp gain (outer ring) by one click to add 6dB gain there, and reduce the inner knob back to the noon position.
If the inner knob is digital gain, indeed there is no difference between using that and using digital gain in your DAW software later. If it's analog, then you could use it to get the highest permissable level into the A/D converter, which might give you slightly better noise figures - but the difference would be extremely subtle, I suspect.
Overall, think of the inner knob as the fader of a mixer channel and the outer ring as the channel trim. But because the trim is stepped, if you did want to gain ride the incoming audio (in particular, raising the gain if the performance level falls), you'd use the inner knob so as not to get 6dB jumps.
