Amazon, as one of several streamers, offers only Flac lossless music. They've fairly recently offered HD when available at no extra cost (I payed an additional $6 a month for HD when first instituted).
A recently released favorite album of mine, Little Feat, Waiting for Columbus, was remastered and offered in HD (24 bit/96khz).
I have ~2,500 CD's I've collected over the past 40 years, ripped with care with good software to Flac.
Choosing between my library (Foobar) and Amazon Music Unlimited, I choose Amazon. Easier, sounds as good or better.
I resort to my library for the esoteric, and that's more than a few with my tastes.