Well it depends on how involved you want to get on the mix down. If you want to go full studio crazy, you could record the tracks raw with no EQ or fader moves or even mutes. Then you'll have to mix the whole show from scratch. This sounds very time consuming but if it's your band making the big live album, it's probably what you want.
On the other hand, here on Taperssection we usually try to capture events as they sound, or perhaps a hyper-real version of that, to quote a recent thread!
Post fader will give you the actual show as the sound mixer mixed it.
The fader is last in line, so post fader will be post EQ (that's good so you don't have to re-create the drum sounds for your remix), and it should be post mutes, so any unused channels (maybe a sax mic when the wind player is on flute) will be nicely blank. You still probably want to check for low level noise when you mix down, since the channels can add up when you have that many!
I found a video which shows a bunch of options for the internal 2-track record selection around the 1:30 mark.
https://youtu.be/mdVcoD5HpAI?t=80Please feel free to ask me more questions. I've mixed bands lots of times, but mostly long ago, so I have not made many multitrack recordings. But I'd like to make more.