I can't answer the servers part of your question.
There are no "premium features", just the option to pay to remove the adverts, but there is "Premium Support".
Pay for Premium Support and you may post in the Premium Support forum where you get the Nabble team providing a faster response to queries and an unspecified amount of the team's time in developing personal edits to the NAML code that generates your forum.
Often such premium support requests are accepted as good additions for the main service and they get rolled out into the main product for everyone to use, so everyone benefits.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.