Why FLAC files are large
FLAC is lossless, so it keeps more audio detail than MP3. That makes it excellent for archives but less convenient for quick sharing.
MP3 or M4A?
Convert FLAC to MP3 for maximum compatibility. Convert FLAC to M4A for Apple-friendly music libraries and compact mobile playback.
Keep the archive copy
If quality matters, keep the original FLAC as your master file and create MP3 or M4A copies for everyday use.