If you keep copying media with your Reaper projects the 20gig will run out soon. If you add wav or mp3 etc.. to your Reaper project, add it from the project folder so you will have it stored. Those and any other renders will be referenced in the project folder.
The whole idea of all this is so you don't have a hard drive full of wav files that Biab and BB Plugin made !!!

You just add sections the same way you normally did using wav renders from Biab, it's just so easy doing all this in Reaper, you can insert/remove bars in Reaper, you can insert new regions, you can copy track sections along with the regions. You can copy track sections from one Tab to another.