Changes in DAC Presentation - Need Advice

Yes, the opticalrendu is wonderful network upgrade, recently upgraded from TPLink FMC to opticalrendu, plays on much higher plane.

As for Macmini. I've used three different macminis over the years, never had a single glitch with Roon. These things are network related if mini optimized as server, therefore, shutting down all those non-critical processes. You do have one major upgrade left to you with mini. Get Uptone MMK with Uptone JS-2, then use Thunderbolt out as ethernet bridge out, you'll have top flight server. Just doing the ethernet out from thunderbolt alone will be of great benefit.

No, I was previously running two TPLink FMC, both with lps going to SOTM SMS200 streamer/roon endpoint. The opticalrendu replaced both last Tplink and sotm, powering with Uptone JS2.

Your issue is wifi, you have to do hard wiring for any HQPlayer, really even for any decent streaming.

https://audiophilestyle.com/forums/topic/30376-a-novel-way-to-massively-improve-the-sq-of-computer-audio-streaming/#comment-613370 This link explains how to use thunderbolt port as second ethernet port for direct ethernet out. I don't know if you're using router with switch or router alone, but you can bypass switch or router post server by doing the direct out thunderbolt port.

Your new routing would be: modem>router>mini>FMC>rendu. You'll have no need of switch ,at least post server with thunderbolt ethernet out. This is quite large sound quality improvement.

First and foremost you have to get hard wired,even long ethernet or coax cable is superior to wifi.