I’m digging in right now. Here’s the deal. With SPDIF, the connection to a DAC is synchronous, and the transport (sender) is the clock. So your DAC is limited to the quality of the incoming signal, improved by whatever jitter reduction it can do. Jitter has a huge analog impact on pulse-amplitude modulation, and therefore on the output.
Now, USB and Ethernet are asynchronous. They just send stuff to a buffer, and the DAC clocks the samples. Much better and less dependent on the sender. However, noise is still a big issues and some folks i trust report differences beyond that - having to do with the quality of the pulse-shape of the USB. never heard this about Ethernet, mostly because its so hard to separate out.
So, does the streamer matter in a network? Not much IMNSHO. But does the networked device that takes in the Ethernet, and spits out the USB matter? Yes apparently, although it should matter less than SPDIF, ** IF AND ONLY IF ** the DAC has a good clock signal.
Streamer - not so much
Network adapter- yes but somewhat vague. Its about jitter and digital noise that impacts jitter i would guess
DAC - yes and it is even more critical that it can generate a good, low jitter clock, since there is none being sent to it (unless you use some franken-protocol like I^2S (inter-IC-signal) which sends signal, ground and clock and was never meant to leave the motherboard.
I plan to get ROON, put it on a low noise, fan-less, trimmed OS computer (aka ROCK) and then use a good USB DAC, and for my (excellent) legacy DACs that use SPDIF only, a quality USB-SPDIF converter like Schiit (new) or a network device like the ALLO.
Its a quagmire. Welcome to the slime.