Since you mention that you are using either QTR or ABW on the same printers, I assume you are talking about using QTR with the OEM Epson Inks, correct? And a few more quick questions:
Have you ever experimented with QTR and Piezography inks? I'm curious how you would compare QTR/OEM Inks with QTR/Piezography Inks.
What tools do you use for making/tweaking your curves (quad files) for use with QTR?
Yes, OEM Epson inks.
Yes, I have experimented with Piezography K7, but not on my printers. In my private opinion, in pair QTR/Piezo, QTR makes the hob even more then Piezo itself, it is enabler for good inks. In most cases I had, difference is not big when comparing OEM to Piezo K7 (both using QTR, but I have not tried Piezo Pro). Difference can be visible when you have many nuances in very light areas or dark ones (high key / low key), but is not large. In all cases you need to learn how to make good curves, what is not easy.
Now, I use Color Munki Photo, well prepared test chart with 51 patches but randomly placed and at least 3x repeated, own algorithm for curve smoothing after Munki scan for linearisation and QTR own built in tool for curve creation.
I do not use external tools now (tried bwmastery.com, but early versions were interface unfriendly - now should be better, and was not very happy when the one I purchased was not allowed to be upgraded to newer one. You can try one, if you want some more colorisation options, since they are hard to achieve by yourself, but you need to remember that it generates not curves as QTR built in tool, but result/final quad files).
QTR own built in tool is quite good once you make long try and error learning, or get a hand from some more advanced users.