The setup that I have uses a SGC as a Roon core, which then connects through my home network via Ethernet. The SGC can also be set up in a few other modes that the Rendu players accept. I then have a network switch with an SFP module that converts the signal to optical and a magenta patch cable to feed into a Signature Rendu, with USB going out to the DAC. This same setup would work with an OpticalRendu as it accepts the same fiber optic input.
In a separate setup, I have another network switch with an SFP module which is connected to an optical converter. The Ethernet gets converted to optical in the switch, then back to Ethernet in the converter, which then feeds the ultraRendu, with USB going out to the DAC.
The advantage of Optical vs ultra is that there are fewer boxes and less setup required. The OpticalRendu also has some other internal improvements, and I expect the new OpticalRendu to have even more.
Just as a note, when ordering parts like the SFP modules, you really need to pay attention to specs: frequency, throughput, compatibility with your switch. They aren't all the same and if you get the wrong module, it won't work. I ended up getting a Cisco SFP from FS.com since I was using Cisco switches, and their tech support e-mailed me to confirm compatibility before they sent it out.