Yes that's all good.
The:
RC770 Bass - Acous bass
RC771 Piano - Acou grand
RC1099 Guitar - Acou Grand Piano
RC490 Strings - Acou Guitar nylon,
are all the RealCharts they have the volume turned down by default, if you double click on them the notation window for that RealTrack will come up. You can also use them for Layering eg: if you set one to a synth or other VSTi Instrument so they play with the RealTrack, you can have a Sax play along with a Guitar or alternate.
Did you try and uncheck "Also Generate RealChart" from the Ctrl+G menu and see if the Drums Generate by themselves ?