As for the position of the gain knob I start at +3 by default and then tweak to taste. This makes the drive more noticeable than at 0 and less annoying than +6 (if +6 is too much for a particular track.)

Usually I end up between 0 and 3 somewhere.

As for which module, it defaults to the S model. I then ask myself "do I want this to be a tad more open/bright? Then I use the N. Do I want it warmer/darker? Then I use the A. If neither sounds better I go back to S. If I still don't like S I will a/b with it bypassed and decide whether to keep it or drop it.

Of course, this is all relevant to musical style and where I want the mix on the continuum between clean and warm/driven.

Peace,

Tunes