If you watch this video you will see how things sync play.
RapidComposerVST is loaded into Biab because the vst sync was finally fixed,
therefore the RapidComposerVST will sync play and send midi to Biab, if RapidComposer did not sync play I would have to drag the midi from the standalone RapidComposer app into Biab, but wait, you can't drag so I would have to import that midi phrase into Biab into the correct bar then playback Biab to see if it fits nicely to that section, if not I will have to import another.

https://www.dropbox.com/s/k7q8ikg7e3pgx0g/Biab-RC-Ample-Bass.mp4?dl=0

Why is this MultiRiff playing in sync to the existing tracks, do you really need that, maybe they can disable that ???
https://www.dropbox.com/s/lopuqjm4lxuixde/RB-Reaper-ReWire.mp4?dl=0