This is not a question, but many. I’ll try to tackle a few. Not from an authoritative position, but from experience.
The first layer of your line of inquiry should not be about the DSJ, per se, but about whether a network endpoint can reliably - and with sufficient quality - have digital music piped to it over a network that is not all hard wired. As apparently stated by sales, it can be hit-or-miss. True. But so can hard wired be, though certainly much less so.
Guarantees of reliable delivery fade away when you start talking about moving your data over radio waves. But that does not necessarily mean it will be unreliable. I’m personally a big fan of hard wiring networks. But life events forced me to abandon my hard wired music delivery system for a largely WiFi based delivery system a few years ago. And OMG what a nightmare it has been. No matter how much money I threw at it, and I’m a network guy by profession. Different kind of networks… but I speak the language, understand the concepts. But my WiFi was a non-stop PITA nonetheless. That said, my music was never impacted by it. That’s why the Gods-of-Digital-Streaming invented buffers. Granted, every digital endpoint will not use buffers, and not all can/will use buffers well. For myself, the only digital streams that come into my DSJ’s Bridge II are from Roon. And Roon’s RAAT protocol takes care of that, and takes care of that very well, IMO. I have zero complaints, relatively speaking. That leads to a discussion of 802.11, aka the IEEE WiFi protocol.
IMO the topology of 802.11 is flawed, and only now the marketplace is seeing what IEEE should have seen 20+ years ago. Specifically, that it was fine when you had a single access point, with sufficient signal strength, without radio interference. But let any one of those three things slip, and it all start to fall apart. That’s where mesh comes in. Not all mesh, mind you… mesh is a topological concept, not a defined standard. So…
You bought Eero. Good for you! Recently I made the jump to three 2nd Gen Eero’s myself, and have never been happier. What USED to work sending music from either my NAS - or the Internet - very reliably, now is just rock solid. Stupid solid. Same government laws regulating how strong my network radio signals could be. But Eero’s mesh implementation kicks butt on what could be achieved under 802.11.
And lest I be unclear… it’s the protocols moving the music that matter. And Roon’s RAAT is good. Those can pick up the slack for momentary radio connectivity problems. I had very, very few of those. Where typical WiFi falls down is not the quick hiccups - those get taken care of by buffers. It’s the problems where it just DOES NOT WORK, for seconds or minutes at a time. And - my friend - IMO that’s were you are going to be just fine for investing in Eero’s. Well done. I’m personally delighted. Zero issues moving music to my DSJ.
Good luck in you decision process. Hope that helped.