Hi, I have returned to post the result of my quest for perfect tone.
I am playing a new Taylor T5 Custom through a TC Helicon Play Acoustic, into the T4s, then on to an L1-1s B2. For vocals a Sennheiser e945 through the same path as the guitar. I have spent countless hours trying to dial in the perfect tone using the Play Acoustic, only ending in frustration. So I tried running the guitar flat through the Play Acoustic and using the T5 preset in the T4s. This was better but still not exactly what I was wanting. But it didn't take long to dial in the tone I was chasing with the zEQ and Para EQ. Just so much better than the Play Acoustic. So now all my Play Acoustic presets are set to flat.So now I have 3 presets that all sound good for the T5 on the T4s, this includes the Bose T5 preset and my 2 custom presets, one using the Bose T5 but modified slightly, and another using the Bose Flat preset that I modified. At present I am thinking I will probably settle on something in between the Bose T5 preset and my modified version of it.
Even the vocals I found the T4s sounded better than the Play Acoustic, using one of the presets and slightly modifying it. I used the Audix OM6 preset and added some Mid, rolled off a bit of bass. I couldn't detect much difference if any between many of the vocal presets, I just used one that sounded about the best.
What I am now using the Play Acoustic for, is mainly harmonies. But also for guitar effects, even though I think I prefer the sound of the Bose ones, it's just more convenient to switch them with them Play Acoustic, as I have a separate preset for every song that I do. Same with vocal effects, my vocal effects can change a lot depending on the song. Would be lovely if Bose built all of this as well into a foot pedal or something? And have it all able to be automated with a backing track like the TC Helicon Voice Live 3 Xtreme, which I have been considering buying. But now I don't know.
Anyway hope this helps someone. And provides useful feedback for Bose.