That's great ! I'm glad you stuck with it and got it sorted. Once you have it all working it will make things so much easier.
You can load the BIab frozen SGU into any varying tempo map and it will automatically fit, so you can add BB tracks to any live recorded band session.
Once you get comfortable with the Reaper scripts there are others that will do so many things you can't do in Biab like instantly change an FX guitar to a DI guitar keeping the same riffs, you can write the chord names as Take Markers into the track and save the track as a template.
Reaper is a great companion for Biab whether you are using the new BBPlugin 6 importing tracks instantly or you prefer to work with the main Biab to build up your songs/tracks and instantly transfer to Reaper.
justanoldmuso prefers to use flac format in his Reaper projects, this allows you to set the file type to use so any Reaper compatible audio/video format that will work if you batch convert the RealTracks and Drums folders to add another format.
This way will also let you change the tracks to Video RealTracks/Drums if you have them.
I haven't look to see if any of the Video RealDrums have Stems now ?