1 USB device at a time, with recognition upon insertion, would be excellent. The problem is: (1) the iPhone continues to be recognized even though it is set to be ignored, and (2) once it has been recognized, even after ejection, something continues to prevent Calibre for recognizing the Kindle.
What plugin do you mean? I'm not aware of having enabled any plugin, and many calibre versions ago, when Calibre first recognized the iPhone, I instructed it to ignore it. What should I be disabling?
And as to only charging: I may be synching the iPhone too, and iTunes may be playing music... Is that a problem>