Matt is correct about MultiStyles. There are more than a few though, my current BIAB version has more than a Thousand PG Music MultiStyles. There are two types of MultiStyles, Global and song specific. Any Style in the StylePicker can be user modified into a song specific or global MultiStyle. They are controlled by Part Markers from the Part Markers drop down menu. This window supports up to 24 style changes, each with two a/b substyles allowing for 48 different drum groove variations per bar... 1,536 variations in 32 measures.
Regarding the issue between what instruments are played to how they play is also possible in BIAB. The method I use most often is to select an artist in the RealTracks Picker and audition the various RealTracks they've produced. There are many instances of artist's having a variety of styles, genres, feel, rhythm and soloist RealTracks using the same instrument that are easily intermingled into a song project.
For instance, the original Legacy Tracks each have 10 additional slots to place alternate RealTrack instruments on them. These instruments can be manipulated by Chorus, Part Markers or number of bars. They also can be manually set by a user.
I've attached screen shots of artist Dwight Sills list of RealTracks that provide 8 different RealTracks of the same guitar being played by the same artist in groups of 4 soloists and 4 rhythms. These tracks can be mixed and matched in any combination onto a single track and will yield a wide dynamic range of music.
Description: Dwight Sills Medley