Hello @Ansgar
Best library seems to be Spotify, Apple and Amazon. Qobuz is missing some artists, and some albums, but their range grows daily, plenty there to have fun with.
Easiest way to see whats missing is to subscribe to Qobuz, first month is free and if you are not in love you can drop it just before the month is over at no cost to you. Quality is definitely there, in my opinion often better than Tidal.
Roon is the best for what it is designed to do, no you don’t need the roon core……laptop, PC, even apple tv can be used. Lots of info on possible hardware options on roon website.
With Tidal, naim has no plans to support MQA, lots of info on pros/cons of MQA can be found here, so if you want to know more search the forum for master quality audio or MQA.
For example;
Apple is also about to launch HiFi from June;
FYI Naim is also working on a Tidal connect.