Biab doesn't use non destructive editing for imported files, it don't reference the source files so you usually get a 32bit wav file attached for each track. The RealTracks just reference the source files so you don't get a massive size.
With midi there is no easy clip editing/moving like in a DAW or EZdrummer so the best thing is use an empty track to import the midi then select all those notes then cut and paste it to the track and position you need it.

You can use Biab as a ReWire Master and use Reaper as a ReWire slave and load all the midi and audio clips into Reaper that will give super easy drag n drop audio/midi and won't have massive file size attached to it as it will just reference the source files. You can even open the SGU in Reaper to give the chord track.
https://www.xtsware.com/?page_id=334