In a Melco NAS set up to a dCS network player the Melco connects directly to the player for local streaming. So the S100 switch only comes into the picture when you are listening to material from the internet including Qobuz or Tidal. In this configuration it is not relevant for local streaming.
Please forget about the noise issue. It is probably a red herring. Basically Melco have not revealed what the switch actually does. It is their trade secret. We know, however, that what they have said is that it is not to do with clock accuracy or similar issues ( as are most other audiophile data switches) but it is to do with “improved data handling” (whatever that means but it isn’t necessarily all to do with noise).
I can tell you that subjectively the sound of Qobuz is significantly improved using the S100 compared with directly from the router. I do not know why but I would not wish to be without it.
Measurements of the S100 that I have seen do show a small reduction in jitter and noise but these seem too small to correlate with the obvious sonic improvement experienced.