The PTA review is under Components, not Digital as I first searched. I agree, magnificent clarity is the first impression I had.
Yes, the volume is controlled either by the remote or by the touchscreen. Can't answer the how, without opening up the case.
I'm still using my DVA Digital Preamp as a DAC, with the output connected to my analog preamp input, so I can also control the system volume with my analog preamp volume control. I do have a D2A which I haven't connected yet. I can tell you I am thoroughly enjoying my digital preamp and am glad I waited for it!