There is a distinct difference between purchased iTunes downloads and Apple Music subscription downloads:
By default, iTunes may not always download the highest possible resolution to save space or time. You can manually adjust these settings on your PC or Mac:
Subscribers have access to higher-tier formats, including Apple Lossless Audio Codec (ALAC) . This provides resolutions ranging from 16-bit/44.1 kHz (CD Quality) up to 24-bit/192 kHz (Hi-Res Lossless) . However, unlike purchased iTunes tracks, these files contain DRM and will only play as long as your subscription is active. Video Download Quality: Movies and TV Shows
All music purchased from the iTunes Store is delivered in 256 kbps AAC (Advanced Audio Coding) format. Known as "iTunes Plus," these files are DRM-free and designed to provide a balance between high sound quality and manageable file sizes. Apple claims this bitrate is virtually indistinguishable from the original studio recordings for most listeners.
The quality of iTunes downloads depends on whether you are purchasing individual tracks from the iTunes Store or downloading content through an Apple Music subscription. While the iTunes Store remains a standard for reliable, high-quality downloads, modern Apple Music features offer significantly higher fidelity through lossless and hi-res options.