1. If using the ARC port on the display is not causing any issues, I wouldn't worry about it.
2. I look at the built-in apps on a display in the same way I look at a display's built-in speakers -- I don't worry about the feature if I'm not using it. It's probably cheaper for manufacturers to...
If all your sources are running through your AVR, then ARC does not come into play and you can ignore it / shut it off on the AVR and display. ARC is basically used as a method to get audio that originates from the display to the AVR via the same HDMI connection that is used to send video from...