Please edit the paths to the certificates, if you want that each box contacts the cloud with its individual certificate.
This is only necessary if the boxes are 8n different households with content that is only available there or the boxes have a different chip and you want to to OTA updates.
You may customize more settings for each box, just copy over them from.the config.ini and prefix it as the mother options in the config.overlay.ini. Not all options will work, but most that make sense.
For example you may set an individual content directory. Beware it may not be visible in the webinterface.