Thanks Giles - this is very helpful
I'm still a little confused regarding the process required to get a particular instrument (say Thor) to peak at -12dBFS. Would your approach be to leave the input gain on the mix channel at 0dB, and only tweak the output volume of the Thor? You said that most of the factory patches are configured to already peak at -12dBFS - this would imply that the volume of the patch, and the input gain should just be left as they are (default). I suspect I'm missing an important point in your response!
So essentially I'm trying to answer the question - do I need to change the instrument volume, or the input gain (or even both) to get to the reference level?
Thanks again - appreciate you taking the time to help out.