The "reboot update" triggers recovery boot mode causing the SoC to search for boot scripts in the first partition on the SD card. The LE boot scripts are then found, which sets params in the vendor u-boot environment to use LE boot files and if you reach Kodi then everything has worked. To revert to CE you will need to trigger recovery boot mode again. In most cases that's done with the toothpick method, which (with SD card removed) will find their boot scripts and set boot params to use CE boot files. On most boxes (but it depends on what customisation was done in vendor u-boot) both OS are tweaking the same boot params to suit themselves which prevents a simple swap between OS(es) by removing the SD card.
The ethmactool-config service creates a unique MAC address based on the CPU serial to avoid issues where vendor code sets the same MAC for all boxes (and users have more than one of the same box causing conflicts) or where the MAC was not set in the factory and changes on each boot. As long as you have a static MAC address "systemctl mask ethmactool-config" will disable the service on future boots and stop the message from showing up.
Not sure about the blue tint, but as long as it doesn't happen on the TV it's not something I'll be interested in chasing. Vendor u-boot does a few weird things.
NB: If the S805 image is AMLMX .. it is pre-Alpha state and is not even remotely supported.