When exporting a MP3 file of a song the bitrate is always 128kbps and the files sound the same to me. I compared a highest quality mp3 export to a lowest quality mp3 export. I cannot tell any differences in the sound and they appear the same in a spectral analyzer. However, they do not null, so they are different.
Another issue with exporting is that the created file always has a generic .file extension, so, I have to rename them with the correct .extension everytime.
A UI request, grey out the quality selection when WAV is selected since the quality selection does not apply to WAV.