I am currently using the UltraPlusPAK for mac and the from what I know, the real tracks in this version are compressed files (i.e., m4a if I'm not mistaken). Is there any bearing if I save the song to AIFF or WAV?

When I make a song using BIAB, I save each instrument to AIFF and I do the final mix using GarageBand for now. I'm planning to use Logic Pro later on.