I imagine you've seen the reference manual, but just in case, it says that there are three transposition table to chhose from when the NTR (Note Transposiition Rule)is set to GUITAR:
ALL-PURPOSE This table covers both strummed- and arpeggio-played sound.
STROKE Suitable for stroke-played sound of the guitar. Some notes may
sound as if it is muted�this is normal condition when the chord is
played on guitar by stroke.
ARPEGGIO Suitable for arpeggio-played sound of the guitar. Using this table,
four notes arpeggio sounds most beautiful.

That is all I know about it at this point, And I think that's probably all we need to know in order to make music with it. Of course we will need to experiment in order to understand how a particular chord responds to the Guitar NTT, but the factory styles use sophisticated examples that are more comples than I will be able to improve upon, so other than revoicing and reassembling, the availble Yamaha styles will be sufficient for me.

I am not the only Yamaha person that reads this site. Your voice is being heard. But I think even though MAC has made a serious resurgence in recent years, most Yamaha customer are still using PC. I could do a survey, so we can know better.