You asked if you should "re-render" in Movie Studio or DVDA. If you rendered to AVI in Movie Studio, then absolutely adjust the bitrate in DVDAS.
If you rendered to MPEG in Movie Studio, then you might want to avoid re-rendering to a different bit rate since this could affect image quality. It would be worth starting over by rendering to AVI in Movie Studio, then letting DVDAS adjust the MPEG-2 bitrate when it completes the DVD.