Tracking is recording. Adding any software effect makes no difference at that point - you can just as easily do it during the mix. Unless you are using the Apollo interface, w/ UAD effects sent before the DAW.
Many people use a limiter (or more likely a compressor) on the main buss during mixing. This came out of mixing through an analog mixer, esp. the SSL w/ built-in effects. Their mix buss comp is very good and mixers used it for their 2 track output. You shouldn't need it for in the box stuff esp., but I bet most of us have, either to raise the vol a little, add a little glue, etc. It does give you an idea of how a song will sound post mastering (louder), you are doing some of the lifting for the master engineer (or process). The down side of this is if you push your mix too hard (-3 dB, say), it gives the mastering engineer vary little room to work w/. It matters less for home mastering, since you will be mixing and mastering, but a hot mix and a little EQ can cause overs, which means using a hard limiter, which means etc. etc. etc. And for most of us it is easier (and better) to break things out into the traditional steps - tracking, mixing, mastering the 2 track. Once you can do that consistently then start breaking the rules. You'll have a better idea of when and why to break them, and not depend upon dumb luck. On the other hand, most compression sounds ... smoother, if it is done in series. If you know what you are doing a little compression while recording gives you a more controlled track, which you can then massage a bit w/ a channel compressor. Then perhaps again as you send it through a buss comp. Then your recording, which has already been slightly compressed a couple of times, goes out to through the master compression before getting another dose during mastering. A few dBs at each step usually sounds better than squashing the devil out of a track w/ Boost during mastering.
If a track is low in volume, your best bet is to normalize it. Not to -.3 dB, but something like -10 to - 6 dB (which is hot in the digital world). Then you can use a compressor/limiter to firm up the sound rather than as a vol knob.
That is the great thing about recording/mixing - there are lots of ways to do the same job. There are plenty of ways to do things right, but just as many to damage the sound of the song. The art is knowing the difference before you print and send it off.
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