Wellllllll.....I am a early Roon adopter with a lifetime purchase..I have HiRez Tidal, I use iTunes for ALAC and I installed Amazon Music last night.  I’ve been using it for a few hours now....My initial impressions are very good.   Selection-excellent, sound quality-excellent (I signed up for UHD), navigation-interface much better than Roon and Tidal.  I don’t like Amazon (the business model) but I gotta say I like this.  Now, I also like Tidal for MQA so I’m not going to doing anything drastic yet...But I’m beginning to have dark thoughts that I could live with one service and Amazon may be it for me....say it ain’t so...RIGHT?
Most will not be hi res.  If they were originally recorded before digital recording, they cannot be high res as the source was not.  Putting them in a high res package, does not improve the resolution.
I can’t stand amazon and usually stay away , but I did install the app and will give the 90 day trail a go . So far I really like the App,and sound quality has been excellent . Amazon’s app blows away Qobuz and I also enjoy it better than Tidal . I have already canceled Qobuz due to the weak library they have , and Tidal will more than likely be next .great job so far Amazon .