You can be a long time away from the ETH with a managed Windows device. The power supply should work but you will need an adapter or different power cable. The warranty applies throughout the world.
You can work offline with your files on the desktop and in the documents folder without ETH network.
You need to connect to VPN to synchronize data from RDS and from your local machine to your network home drive.
Programs from the app store work as well. You can even add new programs with the app store if you are connected to ETH VPN.
You need to connect once a month to the ETH VPN to activate the licenses for Windows and Office and to get Baramundi and Windows Updates.
Local user and administrator
Create a local user for your computer so you can continue to work if your eth user should be disabled. You should be able to use your local administrator account (spadmin).
You can use RDS from any computer. Local printers work with RDS.
If you change your password please follow the instructions here.