@Dave-Huggy-Jones No idea buddy. I only make the occasional plugin. 👍 Not sure what the final plans are for groups. But I'm sure if enough people request something it will be implemented.
As it currently stands, category is hard coded into NodeBB. It will require a lot of work to make the paths custom, but it is a planned feature. So, you will either have to just not change the path or get somebody to change all of the hard coded areas that need to be notified in the site code.