Aside from the chords, there is little you can do about RealTracks or RealDrums. They are audio recordings of a bunch of different phrases from which BIAB and RealBand builds from. For example, if you want an arpeggio in a particular place, you can't specify it. You may be able to find it within the audio tracks but sounds like a lot of work to me. The RealDrums are the biggest leap (for me). No more 'midi sounding' drums. There are a few things you can do such as trading 4s and shots.

Bottom line is if you want a customized song with RealTracks and RealDrums, you will probably have much difficulty. RealBand is you best bet. You may want to listen to the RealTracks and RealDrum files. That will give you a good idea of what you have to work with. They are found in your BB directory under the Drums and RealTracks folders. They are .wma files and can be played in most audio players or imported into a DAW.

Good luck,
R