Yeah at the moment we have it hardcoded so you must be staff to create channels.
I think there is a legit feature request here to allow expanding this to a wider group, that way you could delegate trust to a wider group of people to create channels.
That said:
That is what channels are … I can see you already created a few channels and secured them using your secure categories.
All the people with access to the secure categories now have access to the chat … especially since you already set up chat_allowed_groups appropriately.