When you are publishing your game, you just have to replace the Master Server, and if the Prefab Server is not sharing the same IP/FQDN, then you have to also provide the IP/FQDN for it.
As for the license. The permanent license gives you 1000 CCU (concurrent players connected to the server). You can stack them to increase this limit, so 2 licenses give you 2000 CCU, etc.
If you have 1 license (1000 CCU) and you want to start multiple realms, let's say 2, then by default our Atavism licensing server will divide it equally, so 500 CCU each, but you can set it in the configuration file if you want to split it differently, let's say you have a production server where you want to have 900 CCU, test server with 90 CCU, and development server with 10 CCU, you can use these limits, but the sum of all can't breach your license CCU limit (in this case 1000 CCU if you have one license).