There is no details how to connect video on a specific HDMI
On LE, Kodi does not run under a desktop/windowing environment so display selection is not possible. Instead Kodi will output on the display connector that probed first, and because hardware probe order cannot normally be guaranteed it is not possible to pre-determine which connector will be used.
On a general purpose Linux distro with a desktop/windowing environment you can move the Kodi app window to a specific display and the OS will (or should) remember this, and Kodi will allow you to select a specific display for full-screen output.
In both cases you should be able to select a persistent audio output device in Kodi settings.