While Apple doesn't call it "iTunes Plus" anymore, the backend is the same. When you purchase a song from the Apple Store (not streaming), you get a 256 kbps AAC M4A file, DRM-free.
Unlike earlier M4P files, iTunes Plus tracks can be played on any device supporting AAC, such as Android phones, consoles like the PS5, and modern car stereos. 2. Technical Superiority: AAC vs. MP3 Itunes Plus Aac M4a Sites
Amazon offers MP3 by default, but many artists and labels now supply files to Amazon to match Apple's quality. While Apple doesn't call it "iTunes Plus" anymore,