I save everything in mp3 128kbps. I compared the quality with higher quality and with my setup (Bose speakers & in ear headphones) and with my ears, I can't hear a difference. Opus is more efficient but my source is already in mp3 and I don't gain anything by converting it. If I had to convert from flac, I'd choose opus. 1 4k movie is so big, the size of music doesn't really matter at all.