I hope the Roland BK-7m follow the GS rules on most of it's sounds, so it will sound OK with any modules.

I thought that anyone can play Ketron Yamaha and Roland styles on the same software should be nice.

But I don't know if roland allow the internal styles copy like some other keyboards

About the chord sequencer : you mean, press record on the sequencer, then you play a serie of chords in realtime with the arranger, and the sequecer record it, then press a key on sequencer, and it play back this series of chords at the right time?

For that it need that the the arranger clock allow to be drived by an external clock from it's midi in.

Now that I added the song chords feature to vArranger, allowing to create song entering some chords, maybe I will add the Korg chord seq on vArranger

But on an external arranger, it will depend if the hardware arranger can be drived by an external midi clock