best practices for the xgs series

The good part of SFOS, the OS is always the same, no matter which installation you have. So your configuration looks like a bigger appliance. XGS comes with all features enabled, which greatly increase the performance onboard. 

So simply create your rules and follow the standard start up guides, which will give you the insights. https://docs.sophos.com/nsg/sophos-firewall/18.5/Help/en-us/webhelp/onlinehelp/StartupHelp/ControlCenterOverview/index.html