When I wrote my last post I thought that the reputations of the Schiit and Rogue preamps were sufficiently well established that I failed to say the following. Remember that my personal judgments are, as best as I can, against live unamplified music. The inexpensive Schiit preamp with tubes was a very clear improvement over the fine transistor one. It was then that I discovered that I MUST have a balance control, which has gone out of favor on many excellent preamps. So I went to the far more expensive Rogue--I needed balanced outputs as well. It proved to be an even greater improvement than was the first change. A testament perhaps to the value of the Rogue’s extremely strong power supply (LPS, of course) in delivering sound quality. I am very happy with the Rogue listening to all recorded music. That should answer question 2.
No doubt you are focusing on the THD number. First I would refer you to all the discussion here (and elsewhere) about the uselessness of the industry type of specification next to the experience of actually listening. One of the problems with the published THD number is that harmonic distortion may take on different shapes--all hidden in the industry-standard number. Generally in units with tubes, the major factor here is that the THD is principally in the second harmonic.
It has long been a controversy in audio. Does the slight bit of second harmonic that is ordinarily introduced by tubes "distort" the sound so as to make it less like the real thing, live music? Or does it restore an element of the sound that is ordinarily diminished slightly in the recording and reproducing process with the result of sounding more like the real thing? And so one can choose solid state or tubes conforming to your answers here, and I chose a tube preamp that is know for having that fine attribute of tubes, but mildly so. I believe that answers your first question. We touched upon a similar issue a while back when discussing feedback in solid state components.
To answer the third question directly. I don’t spend much time on the kind of comparison you ask about. But for a short while when I was experimenting with streaming I was receiving Tidal and Amazon Music at the same time and testing the streams with MusicScope. A series of Shostakovitch symphonic recordings with the Boston Symphony Orchestra under Nelsons was the being released. Tidal had them at 16/44 and Amazon had them at 24/48. While the differences were subtle, they were sufficiently distinct.