I am peculiarly situated to answer your question as I am currently using the Mini and still kept my Vault for a second set up. I also am streaming premium versions of Qobuz, Tidal and Amazon HD. In contrast to the above, in my view the Mini is a significant step up; however your last question may render that moot. The Lumin App is glitchy and the support I have gotten has been lousy. BLUOS is a much superior app and works much better in my experience. That said I am running ROON through the Mini with tremendous results. Hope that helps.
Lumin U2 Mini
I was hoping to get user feedback on the Lumin U2 Mini. I currently have a Vault 2i and have really enjoyed it. The Lumin looks appealing to me for several reasons . I was hoping to find a server that would allow me to pull my Vault files through the network but it seems Bluesound is a closed ecosystem and doesn’t support UPnP . That said I noticed the Lumin has digital inputs . This would allow me to use anything in the Vault through the Lumin and my DAC
I was also wondering how the Lumin app works compared to BluOS. Thanks !