1) A well-designed analog volume control can always outperform a digital volume control, as they note "if they [the analog volume controls] have a lower noisefloor than the DAC itself." That is correct, but it is non-trivial given that the noisefloor of the nicer modern DACs are essentially a few dB above the thermal noise of the resistors involved! I've encountered many analog volume controls over the years (even ones made by reputable manufacturers), that were quite noisey. Low-noise volume control design is not a dark art, but it's not guaranteed either. So this point is technically correct in the abstract, but there's no guarantee that the volume knob on any particular piece of kit is going to be lower noise than a well-designed digital volume control (and it might well be quite a bit worse).
If you are looking at a volume control integrated into the DAC itself, I believe you are limited to either Lavry or Burson DACs if you want a really good analog volume control that has the potential to outperform a digital one.
Other than that, I guess there are maybe high-end pre-amps which do analog volume control well, but most people are eliminating pre-amps by using DACs that have an internal volume control these days.
2) If you're reproducing 16-bit music on a 24-bit (or 32-bit) DAC, the "performance" of the volume control is entirely irrelevant unless it compromises the 96dB envelope of the original recording. Put another way, even if you lose 40dB of dynamic range using the digital volume control on a 24-bit DAC, you still have 104dB of dynamic range, which is more than the source material. Because there is no dynamic range to "lose," the performance of the volume control is a red herring. With 24-bit music you may be discarding some very quiet bits, but whether bits that are effectively beyond the dynamic range of human hearing (outside of a lab) are important or not is something each of us will have to decide for ourselves.
I think that part of this is also that the ESS DAC can reduce its output voltage - to a point - before switching to entirely digital volume control, which is why it would be better to use the DAC's internal volume control rather than an external one.
The internal volume calculations are also performed with 48-bit precision rather than being limited to the 32-bit, or more commonly, 24-bit output from a PC.
But in the real-world, most of this does not matter too much. I agree that most of the time a well designed and properly dithered digital volume control will not have a negative effect on audio quality with a 24-bit DAC until you have a significant reduction in volume. When I say significant, I'd say that most people would not start to notice the effects until you are below -60dB.
If your DAC is capable of ear-splitting or potentially speaker-damaging levels at 100% volume, I would suggest investing in fixed-level passive attenuators.
That way you can keep the digital volume level higher, which increases the signal-to-noise ratio (SNR) and there should not be any of the negative effects that you could have with a variable analog volume control.
Of course another option would be to replace the amplifier with one which does not have so much gain - which may bring other improvements, but that is going to be considerably more expensive.
With the Chord Hugo specifically, you are probably better off using its internal digital volume control, rather than JRiver's. I'd still leave Volume Leveling enabled, and you probably still want to combine that with passive attenuators so that you can use a higher digital volume level on the DAC though.