Limitations are on the website - https://grapheneos.org/articles/
I don't care about google pay/wallet or android auto. My credit union's app does work fine, but even if it didn't, I'd still use GOS. It's great.
I rip and convert to FLAC primarily for the reasons you stated, but I also have to convert to MP3 when I want to play music from an SD card on my car's head unit.