I’m not Craig but I may be able to offer some guidance. Multiple high speed network availability usually isn’t available for most homeowners. If you’re lucky, you may have two vendors to choose from but more likely than not, it’s just a single high speed vendor. And if you do have a single vendor, most SOHO routers (which for home owners are usually just residential Wifi routers or vendor provided modems) don’t have the capability of programming to handle this. Craig’s network with a Unifi router backbone can likely do multiple paths to the outside world. But when you design this, the secondary connection is usually just a fall back in case the other one fails.
Three years ago I helped a medical practice in my town upgrade their network capabilities and do better links to their satellite offices. We switched vendors to high speed connections from a well known national provider (Level 3) and we kept Comcast Business as a fall back on the main router if Level 3 was unavailable. It was not used as a subset of their traffic. Could you do static routing to do that? Sure, but it’s something you have to maintain yourself and you never know if someone upstream is going to change the path.
I don’t know if Craig designed his own network or brought someone in but it’s clear that whoever did it knew what they were doing and planned for the future. Are some parts of it overkill? Probably. But his provided schematic is sound…I have a lower powered version of it myself. I’m just doing gigabit Ethernet on a Netgear GS116 16 port switch with 8 and 5 port Netgear gigabit switches in other places in my home (home theater, office, etc). I have Comcast Gigabit as well. Wifi is a hodge podge of Apple devices and one Netgear R8000 (which I later realized cannot saturate gigabit Ethernet so it’s not central to my network anymore) I also have about 50 TB of storage available for media, just with two Drobos, one old (Gen 2, firewire), one new (5D3, USB3) hooked up to an elderly 2008 Mac Pro for file, Plex, Roon and HQPlayer service. Would I like some upgrades? Sure. But for now, this gets the job done largely.
The biggest strain on my network is 4K streaming to two different LG OLED TVs from the outside world or from ripped 4K Blu Rays on the Plex server. But wired gigabit Ethernet works very well and I’ve tested it running multiple high quality streams to every TV, laptop, and iOS device simultaneously. It’s unclear how close I am to saturation on my switches since everything is unmanaged right now. But so far, it all works.
And for the sake of staying on topic, I have three Roon zones matching my three music zones.
Home theater (multichannel):
Oppo 205
2009 Macbook running Windows 10 (Roon + HQPlayer NAA) feeding Oppo 205 via USB
Marantz 7703 (Oppo has HDMI and analog connections to it)
Amps are too embarrassing to mention
Living Room (2 channel):
Oppo HA-2 portable DAC (if an Oppo 205 frees up on the final list, I’m buying one for this spot)
2008 iMac running Windows 10 (Roon + HQPlayer NAA) feeding Oppo HA-2 via USB. This is a music kiosk machine for the room
Audible Illusions Modulus 3 tube pre-amp
Parasound HCA-2200 two channel amp
Sun Room listening area (multichannel):
Denon X2000 receiver
2010 Mac Mini hacked to run macos Mojave beta (Roon) feeding the Denon via HDMI
Servers:
2008 Mac Pro High Sierra w/Drobo Gen 2 (10 TB effective space) + Drobo 5D3 (40 TB effective space) running Roon Core, Plex, iTunes, file share, DNS, HQPlayer for Home Theater
2006 Mac Pro El Capitan (HQPlayer for Living Room)
2008 Dell Poweredge 2900 (Windows Server 2012 R2 file service)
As you can see, a lot of my enterprise is done on the cheap with aging equipment often repurposed in ways not normally supported (Windows 10 on unsupported Macs for example mainly for ASIO USB support). But with a solid wired network, it’s all pretty good. The Sunroom doesn’t have a proper outbound DAC but with an old Mac with HDMI and a receiver, I can make do and even do multichannel music through Roon.