For lack of anywhere better to mention it, I found that my NAS audio out jack allows bit perfect output to my stereo receiver. I can thus use this as the main endpoint and bypass the sideloaded app on the shield tv.
My zenpad 3s 10 provides pretty decent output on its own, but does experience some occasional playback stutter that I haven’t yet managed to completely work out.
This all adds up to a pretty decent hybrid library access and overall UX leveraged mostly on the roon/tidal integration and metadata object database.
Plex is somewhat doing its job of offsite serving, and with a DAP in the mix all in all my access is ok. Not totally all integrated and seamless how I want it, but getting there. Perhaps one day Roon will cross the home/external threshold for the ultimate unified system.