I just read Massive's article on tracking too hot...
I'm going under the "no stupid question" assumption, here.

Let's say that I've tracked to -12dbFS, then in my DAW I increase the gain by 10db (not moving the fader, but processing the track to increase the gain).
Is that the same as tracking at -2dbFS?
Nobody so far seems to have mentioned what the real difference will be. Recording 10db lower will increase the noise from your A/D converter by 10db.
That 10db of extra noise may or may not be significant in the context of the stuff you're recording but that's what will happen, whether you can hear it or not in a particular instance.
Whether the track will overload your master output is very much a secondary issue. I personally wouldnt be reducing tracking level by 10db just to avoid possibly overloading the master output later on.
The important thing is to get a track which is neither noisy nor clips. If your track file doesnt clip, it's not been recorded too hot. If it does clip it was recorded too hot.
You dont get any audio brownie points for boasting, "hey I avoided clipping by more db's than you avoided clipping."
The way to get the best headroom is to look equally at the other end, the "footroom", ie: the noise floor of your A/D converter. The idea is to let the baseline noise in your mic/pre combination
just mask out the converter noise. There is no point in tracking with more gain than that, even if your track never peaks above -30dbFS. Tracking louder just robs you of potential headroom. Of course that assumes your mic/pre combination has that headroom itself.
Unfortunately discussions on this subject nearly always omit the A/D noise floor issue and concentrate on setting figures for tracking relative to 0dbFS. That's only half the story.
Read Stefan Kudelski on this in his old Nagra recorder manuals. He made the point that increasing preamp gain beyond say "8" on a particular recorder's gain dial would do nothing but rob you of headroom.
These days we're so spoiled for headroom that we can often get away with not even worrying about the bottom end (the noise end) of the equation.
I come from an older time when headroom really was in limited supply.