All this LMS and info about local playback dont make sense when he has said multiple of times that he only use Tidal and Spotify.It's not that complicated. For local music, you just need a music service. Let it scan the music. Then the Wiim connects to this music service, and you can browse your music.
How easy or difficult you want it, is up to you. A NAS with music service is the easiest, as that is all in one box that stores your music and is the music server.
I just moved the music server to another box (Pi) for various reasons.
If Wiim produced a server/streamer all in one for affordable price, they'll clear up. Ideally 2.5" and 3.5" HDD storage.
Also for you to have local music of your own music, you would need to rip and encode your own music. DBpoweramp is probably the easiest to use, that'll do both, and encode to lossless flac. It'll read in your CD's, download tag information (artist, album, track number, track title, genre etc)
Roon is fine if someone would like to combine local library and streamingservices like Tidal/Qobuz. But when you only use Tidal/Spotify its better with a Connect-solution. Maybe you can use the Xiaomi only for display, but I dont know so try to Google it