We made one AE project and imported each of our projects to it for final composing and editing, and added a track. We tried a few and adjusted the beginning until it matched our video, and added a fade-out at the end of the song as the credits play. We adjusted all the fonts to match each other in size, scale, style, height, and alignment. We also changed the positions of many objects so they align with a fairly standard grid.
Initially, our audio quality was extremely poor so we adjusted the audio settings to 96 kHz and 32-bit which made it sound much more like the original song.