You can't do it like you could with MIDI. They are audio tracks.

There are some tricks for shots and holds, using BiaB features. Realtracks can be generated there and brought into RB for DAW use, BTW.

They are audio tracks, so audio type editing is possible, but you can't go in and change a snare to a tom or anything like that.
Realdrums come as stereo files, already mixed together.
Realtracks are individual intruments, sometimes in stereo sometimes in mono, but they are audio.
You can edit audio in RB about as much as most other DAWs, but you can not go in and 'rewrite' a part. You can regenerate it (over and over) and get different variations, but not total control if that is what you are asking.

One plus RB has is that you can just select a certain lick you don't like and regenerate that section. So you can pick from variations.
One trick I'll use occasionally is to generate a bunch of tracks of drums, then pick thru and copy/paste different sections that I like. So, being creative, you can do a lot; you're not 'stuck with it', but you don't get total control like you do with MIDI.
Sometimes you can even accomplish what you want by actually using MIDI in conjunction with a realtrack (ie add a cymbal at a certain point) but now I'm probably confusing you..

I do not work here, but the benefits are still awesome
Make your sound your own!