MP2 is less efficient than MP3 and has patchy support on phones. FLAC keeps full quality at about half the size of WAV. An MP2 file usually holds MPEG-1 Layer II. MP2 is at home in broadcast radio and television audio; FLAC is the usual choice for archiving music at full quality. FLAC cannot bring back detail that MP2 compression already removed; it simply stores the result without further loss, in a larger file.
The defaults suit most files. Under Options you can trim the start and end.
This pair uses the compatibility engine, ffmpeg built for the browser, because MP2 is not handled by the browser's built-in codecs. It is a one-off download of about 10 MB that the browser keeps, it is slower than the built-in codecs, and it takes files up to 1 GB.