If it is for cd or universal media player format you ditter and save your mix to 16 bits 44.1.
If it is for archiving or postmastering (if you send it to a mastering company) you bettter render to 24 bit or higher, samplerate same as project audio (no conversion), no exessive limiting or maximizing (yet 
) if possible.
In general: as long as you don’t compress (mp3) or use DRM (WMA) , most file formats are “sort of equal” as you can always convert. Lossless (Flac) is also fine as you can restore to uncompressed audio at wish.