I have an Innous Zen Mk3 and Devialet 250 Expert Pro. So both ethernet and usb are options.
First off I used ethernet direct from the Innuos to the Devialet. It worked fine, then stopped working this weekend. I have no idea why. So as a stop-gap I used usb direct from the Innuos. This sounded excellent because the Innuos Zen has an ultra low noise usb output, but there are practical disadvantages in that Devialet currently does not operate auto-detect in usb mode. So with usb you actually have to switch the Devialet on and off, whereas with an ethernet input if you select it in Roon it will switch Devialet on and Devialet will go to sleep 20 minutes after the signal ends.
So I was keen to get the ethernet connection back working.
Coincidentally, I had bought a few items to insert an optical bridge - a refurbished Cisco 3560 Poe-8 switch, a TPLink ethernet/optical converter, an SFP module and an optical cable. I believe this is the sort of thing PSA are building in to their new server. The DIY route has cost me £120 (about $160).
The important thing is the separate dedicated switch. This is fed with data from a router (into the dual port) and both the Innuos and the Devialet are connected. Nothing else is plugged in. It works perfectly. Note that I am not using the streaming ethernet output on the Innuos.
As the connection is with the Devialet streaming card, it should be exactly the same as the Bridge.
What you don’t want to do is connect both the Bridge and the Innuos into the back of a multi-port router. I found this caused havoc as the connection is not solid and Roon goes bezerk.