Opus 128Kbps: Excellent compression, highest quality, best choice for offline listening (Recommended Format)
MP3: Inefficent compression, appropriate if compatibility with older players is needed
FLAC: Lossless and compressed, best choice for archival
ALAC: Lossless and compressed, if you exclusively use Apple products choose this over FLAC
AAC: Average compression, appropriate if your player does not support better formats