<< I would like to know if there's any commands or settings, which can change the music STYLE within one song more "Smoothly"? >>Yes. BIAB has at least two tools that will do specifically what you're asking.
1. MultiStylesPG Music staff use MultiStyles a lot in demos and have a large amount of MultiStyles in the StylePicker. My version of BIAB has more than a thousand PG Music developed MultiStyles. More importantly, MultiStyles are ridiculously easy for users to turn ANY style into a MultiStyle. MultiStyles are a great way to customize a song and very versatile in arranging a song, increasing the number of instruments RealTrack instruments beyond the 7 available tracks in the BIAB Mixer. Providing Multiple soloists in a song and also making it easy to re-arrange sections and change song forms in a project.
BIAB recognizes MultiStyles through Part Markers and the BIAB algorithm program selects audio snippets that are appropriate for the upcoming changes because it 'reads ahead' these changes from the Part Markers in the song's Chord Chart the same as it interprets Chords and automatically creates smooth transitions.
2. Medley MakerA little known and underused tool. But it is very powerful and super easy to use. Unfortunately it's always been marketed by PG Music as a one trick pony for accompaniment and entertainment, tucked away down a menu trail and overlooked by nearly everyone. It's also an amazing song project programming tool.
First, it can literally allow tasks that are impossible to do in a BIAB project to easily be done in BIAB by converting that task so BIAB recognizes it as individual songs independent of each other but the user has programmed each song to be a BIAB project song section.
Second, Medley Maker works as good with a single song as it does a series of individual songs. This allows a user to assign various sections of a single project as a list of songs so various song forms can moved and auditioned in various arrangements.
Medley Maker automatically creates transitions between each song regardless of genre, style, feel, tempo or time signature. There are two limitations; A Medley can't begin in 3/4 time and the 255 bar limit applies. Transitions from 0 to 16 bars can be selected and a user can replace the auto generated transition chords manually.
To find PG Music created MultiStyles:
StylePicker - Search using +
To access the Medley Maker:
From the Main Screen Chord Chart, Tools, Song Form\Medley Maker
Tutorial:
BIAB for Windows Medley Maker Screenshots: