One more before bed time 
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My point destilled (liked that ) is:
0VU is the most optimal level for the most pro analog gear (pre-amps, compressors, eq’s etc.).
Most digital DAW’s and plugins are calibrated to 0VU = -18dBFS, and therefore many plugins that emulates analog gear has been calibrated the exact same way.
We are obviously talking about RMS levels, not peaking. Hover your signal around 0VU and you are good to go.
The easisest “translation” (my rules of thumb when teaching) if you do not use a VU meter (you really should) are these:
For percussive sounds (drums/sharp transients) is to use a peak level at -6dB .
For Signals like distorted guitars, long sustaining organ parts etc, use peak levels at -12 to -18 dBFS.
This is due to the nature that:
Long sustaining (and compressed) signals will (and should) have a lower peak level while reading the same 0VU as short transient full signals.
Added bonus: Following the above “rules” you will be able to have you faders closer to 0 in your DAW, providing you a much better resolution (more precise fader moves) than lower down the scale (due to the Logarithmic dB scale).
There are excellent VU meter plugins out there (will provide tomorrow).
By for now, it’s soon midnight in Norway. Good night.