correction - iPhones use AAC (in addition to the mandatory SBC). I'm not aware that MP3 is used as a bluetooth codec.

and I agree that codec should not be a starting point. If you can use anything other than SBC, which is crap, the codec will be a fairly minor aspect of sound quality relative to the quality of the earbuds themselves (The most likely place you'd run into that is if you use a Windows 10 computer with BT headphones that don't support AptX, Win10 doesn't support AAC over bluetooth, that was added in 11). That's to say nothing about its non-audible qualities; bluetooth stuff can be super buggy/glitchy.

I'm not aware that anything on the market supports lossless yet.