It depends on what you are trying to do with your set up.
This is how I work it:
I am mostly recording live jams so I run all mics into my mixer which runs a mix out to my PA (as well as monitor mixes etc).
For the mics I want to record I am using a mic splitter on the 1st 8 since the Tascam has the XLR inputs, then I use direct outs from my mixer for the other channels into the 1/4 jack inputs on the Tascam. (I would have preferred an option with no XLR inputs myself so I could use all direct outs from the mixer).
I run the stereo outs from the Tascam into a pair of channels on my mixer so they too can go to the PA. I only play them back if we are overdubbing (if there is anything to play back to).
When doing one instrument at a time (like a guitar overdub) nothing goes to the PA and instead I put the playback mix into headphones so there is no bleed on the new guitar (or vocal or whatever) track.
I never change or re-route my inputs. They are always left set up the same way. Then it is just up to how I rig my mixer/PA sends depending on what I want to hear (or what I want to send to another person).
I haven't added it in yet but I need to add a headphone amp. Then I'll route outputs from the Aux mixes on the mixer for individual headphone or live personal monitor mixes.
And one day I'd like to get another mixer that has direct outs for 16 channels, use an adapter on the Tascam XLR inputs and run everything the same way (instead of splitting some XLR lines). But that is a $1400 purchase away
