Yamaha type styles consist mainly of a MIDI file. The first bar contains the controllers and patches to set up the voices in the channels used for accompaniment (9-16). The remaining bars contain the accompaniment for the variations named in the marker event that precedes each variation.
To tweak the styles (adjust to sound best with the synthsizer you use) you probably just need to change a few events in the first bar. A lot of tweaking is automated when you set "synthesizer compatibility" and "Style loudness correction" in Preferences.
The easiest way to create your own style would be to start with one of the included styles and then cut and paste notes from the Sequencer to the variations in the Style Editor. For fine tuning press the Style Data button to adjust the transposition rules that apply to this style.
Styles edited in OMB can be played on Yamaha keyboards like the Tyros.