There are those that would say,
" Observe 0dBu at all times "

For many in Broadcast 0dB would be lined up to -20 or -18dBFS
and others that would go for -14dBFS.

In digital the one thing you do know is 0dBFS is at the top of the scale and so when recording no peak can go over this. Only you can decide if an over can be lived with and likewise where you set you RMS level wil depend on your work flow and you external analog equipment and how it is trimmed.

We have been over this so many times since the birth of digital and DAWs.

Now you will include -10dB unbalanced equipment and it all gets harder, if not impossible to have one single solution.

It might be better to talk about specific combinations or problems.