Simplicity doesn't guarantee great tone at manageable volumes, and IMO attenuation and/or re-amping in your chain throws the simplicity you may have started with in the bin.
Nothing guarantees transparency, but simplicity often helps.
Attenuation is something one pays a price for, but there are a few that minimize the hit. However, I don’t own one.
Re-amping, done well, can sound extremely transparent. It depends on the quality of the gear you’re using.
I’ve almost always used an Avalon U5, plugged its output into recording devices, and used its “thru” output to create a split to go straight to the amp or pedalboard. The Avalon is a Class A, transistor device that I think sounds wonderfully transparent. Also great for basses. They sound gorgeous through one.
Because the signal is buffered with a very high end buffer, a beautiful signal hits the amp with no hit in frequency loss, and the direct signal is clean and great sounding. There’s an onboard EQ if you need it as well that can be switched out of the circuit.
You can also run an amp’s output into it, provided that a load is connected to it. This is something I haven’t tried.
So you have the best of both worlds: A very strong original recording of an amp, live, and a direct signal in case you want to re-amp. While you do have A/D and D/A conversion if you’re using a DAW to record the signal, at 24 bit/96K or better it’s still pretty darn good (depending on your converters, of course).
There are some high end re-amping boxes that don’t alter the signal. Avalon makes a mic preamp called the V5 that’s also a direct box and a re-amping box; it’s a superb thing to work with, but there are others.
However, I haven’t had good results with some re-amping systems, such as the Radial, that I don’t find transparent.
In this regard, Two Rocks meet the specification, and can be run at most volumes using their master volumes or send/return level controls; but as you say, none of them could be described as simpler designs.
The T-Rs are wonderful amps, and I loved the ones I had. The Custom Reverb Artist Sigs were great amps, but not quite voiced as I’d have liked for what I was doing, hence the HXDA purchase. Still, they’re fantastic to work with in most regards. I had 6 of them over the ten years I was a T-R player exclusively.
If they ever reissue the Onyx or make something like it, I’ll be on it like white on rice.
As with most amps, opening up the Master Volume lets the TRs breathe a little better, and I think that improves the sound. But that’s LOUD. I used the Master judiciously, and used a gobo with the amps to reduce the volume in the studio, but also ran speaker cables into the recoding booth with a cab, with the head in the control room back when I had that kind of studio setup.
I didn’t notice any loss in tone with a 25 foot speaker cable of high quality, so there’s that (in fact, with the KHE switch box, I use mostly the PRS/Van Damme speaker cables from the heads to the KHE, and the KHE to the cabs, so some of the connections are running through as much as 50 feet of speaker cable, plus the switch box, with no loss of signal that I can discern. The demos of the amps are all through the KHE. I blame high quality Swiss engineering/manufacture for making a great switcher

. Some of my speaker cables are DH Labs T-14, also great and a titch more hi-fi sounding in the mids, but very expensive).
The best sound I ever recorded with one of my Two Rocks was at a studio I booked. I plugged my Onyx into the studio’s vintage late ‘60s Marshall 4x12. It was a wonderful sound, and the studio’s recording room really let it open up. I’ve never been able to top it. The owner had restored an old tube console and had a floor to ceiling rack of tube gear that he’d restored. It sounded great, I was mightily impressed!