find mp2 files

is it possible to output a list with all mp2 coded files or better all not-mp3-coded files?
If yes, how do i do that?

Several options:
Use columns in the files list, with e.g. %_codec% as value.
Or filter for files with a certain extension, e.g.
NOT %_filename_ext% HAS mp3

You will only see files that are actually read by MP3tag. See File>Options>Tags for the list of file extensions.