Fade or Automate? What's the difference?

..and if you have a comp/lim working a fade (out) won't get in real effect until those stop working

Correct Sir💯🤘 clip gain can be used as well. An aux track fade out is the proper work flow for fade outs in pro tools... like you say if you volume fade out the master fader in PT this will affect the amount of limiting and compression of the overall mix.

NoFilterChuck
The volume fader on master faders in pro tools is pre insert therefore lowering or raising the master fader will increase compression/ limiting or decrease compression limiting.

On audio and aux tracks the volume automation/ fader is post insert so fading the volume out does not change your compression or limiting. Just like raising the fader or adding volume via will not affect or make them plugins compress more. This is why you do vocal rides or whatever rides on auxes or audio tracks ....

Master fader -> volume fader/ automation -> plugin ( pre insert )
Audio and Aux-> clip gain -> plugin -> volume fader/ automation (post insert )

I don't know about the master fader, but in Logic the track faders are post insert.  I just did a search and watched this MusicTechGuy video. Geesh, I've learned so much from watching his Logic tutorials - always time well spent. His videos go from basic to pretty advanced stuff. He always explains a feature concisely and then shows you how to use it.  In the video he gave a bit of an explaination of signal path. Anyway, I know it's a non-sequitor, but I realized I should have my meters in pre-fader mode or at least be checking on it in pre-fader mode when I'm toying with plugs.

So I think in Logic inserts are 'pre fader,' and meaning that as you bring the fader down with automation, they continue to get hit full strength by and process whatever's on the track, but their output attenuates with the fader motion.  This could be a reason not to put a reverb on an insert if you are doing a lot of hard automation.

Sends default to "post pan" in Logic, which I'm pretty sure is also pre-fader, so an automated fader sliding down should not affect the amount of signal that's being sent to the whatever buss the send is assigned to.  If you use sends for reverb as I do, I think this means you could end up with a stronger verb tail than you might want because the verb sees a hot signal even as you pull the fader down.  Since I only use sends for Reverb, I've been changing a lot of my Sends to post fader.

As far as using the fade tool is concerned, I'm thinking the fade tool is pre-insert, which I think means that as you fade out the amount of signal hitting the send fades out proportionally.  I think this is desirable.

So to summarize, I think if you make your sends post fader then it doesn't matter which one you use.  What's nice is you can assign where the sends are not just on a track basis, but by individual send.

Somebody please let me know if what I'm saying is wrong!  Chuck, you're a Logic user, right?