Hello Ted,
Yes I did own a PK400. It may be fine for home use and if you are already familiar with the Orla system and familiar with draw bar settings. It has great organ and accordion sounds. The styles are limited and not editable as I recall. There is not much scrollong through pages as everything is pretty much on the panel, hundreds of buttons and combinations thereof - Not really condusive to gigging - unless, as I said, you're already familiar with the Orla modules. And, it weighs about 70 lbs!
The arranger's chord changes follow the chord button as a default but I'm pretty sure you could change the settings to follow the bass buttons and/or both.
I bought it and sold it about 8-9 years ago. It was yet another piece of equipment to solve all my needs - forever. My wife has heard that line dozens of times over the years.
Ciao,
Jerry