Regarding harmony added to the right hand notes when playing a chord, The idea behind this is to add extra notes to a single right hand note. It is not meant for you play more 2 or 3 notes because the harmony feature is bound to get confused, if you are playing 2 or 3 notes why have the harmony on at all.
Of my previous keyboards Korg, Roland & Yamaha, the Yamaha gives a cleaner harmony to a single right hand note.

Graham UK