If you are are a retired electrical engineer, then you should understand the technology enough to know that it does not take that great a clock to achieve THD and IMD well below the tube output stage on your DAC and possibly other equipment.
Blanket statements about what distortion does cannot be made. It depends on the order of harmonics and the level. Tubes do tend to lend a distortion that generates pleasant higher frequencies and can result in both a slight perception of increased volume, more substantial highs, and greater "air", which helps with the perception of greater soundstage width. Not accuracy, but width. Frequency response anomalies can also give the impression of more width, and height (or less). These are not guesses. These are studied and known.
That you highlight ASR specifically, is a false premise. ASR takes measurements. The conclusions are make are all from the decades of research that has been done on how sound is perceived. ASR has no influence on interpretation in that regard.
Depth perception is almost exclusively a function of differential volume, and intentional reverb. If you are getting more that what is in the recording, then it could be pleasant, but not accurate. Nothing, absolutely nothing in your electronics takes as long to settle as your room, followed by your speakers. Again, frequency response anomalies including some reduced bass, if bass is slow to settle in your rooom or you have nodes can help.
w.r.t. the power supply, at least for the DAC, that is entirely a function of the DAC itself. If the DAC is well designed with good supply filtering, then it will achieve accurate performance well beyond the Audionote, purely by architecture. The one issue that does come into play with lower end DACs, and even higher end DACs, is ground conducted noise. That can be addressed easily for <$100.
W.r.t. the DAC and settling time, frequency response defines settling time 100%. Electrical engineers know this. Also w.r.t. the DAC, solid state DACs almost as a rule have much lower output impedance. If you were talking about speakers, settling time is measured, and if you are talking about amps, again, frequency response and phase defines settling time, and 4 ohm frequency response w.r.t. 8 ohm can tell you everything you need to know about output impedance. Invariably, for most speakers, most solid state amps are not remotely the cause of settling time, though with tube amps that can come into play. This is basic audio EE.
The article you linked only speakers to linear regulators, and though they spent much time, it is rather amateur in its process. The conclusion talks about RFI, EMI, etc. (all at frequencies well beyond what they tested), and then goes on to make a test with 1V on a 25V rail, and well beyond what would typically be experienced, and well beyond what you would see in a 5V USB wall-wort of even middling quality.
What is above only provides crude details. My circuit, in a DAC, starts with a regulated power supply, then likely adds regulation, then adds RC or even RLC filters, with the net result that by the time you get to circuits that matter, power supply noise is near non-existent. Again basic EE stuff.
The proof is in the puddling so to speak though because the other thing that rejects power supply noise is feedback. Any test I have seen of Audionote DACs has indicated noise in the output at twice the line frequency plus harmonics, where many low cost DACs have this well under control even with low cost supplies. That tube output stage requires a whole lot more to keep it happy.
Best minds in the field? Do you truly believe that John Walton is one of the best minds in linear analog electronics? Really?
