First, need clarification-If they’re giving you 5.1 those are NOT stems. You’re getting channels mixed as they appear in theater, tv, etc.
Stems are the sources that are mixed to 5.1
So figure that out first.
————————-
If it were me I’d edit as is with all tracks. You can set audio monitoring to just hear dialog and M&E tracks because your sound mixer will most likely recut the music.
Sound guys aren’t afraid of many tracks. In fact the more, the better!
If he can read Premiere projects, send that along with OMF you export and the source clips. Make sure you don’t change filenames, timecode, etc so everything will link up.