Different custom feeds? Categories?

It looks like a single custom feed endpoint (wprss) can be specified. I am trying to demo Categories and other features to find out if there’s a way to supply many different custom feeds, either by keyword, user, category, or something else. E.g. <site>/nascar/wprss, <site>/cooking/wprss, <site>/scorpions/rss, etc.

Also, in a related matter, if I go to View the items within a Category, or to View the Category itself in the front-end of one of your provisioned demo sites, I get 404s.

Thanks for information
Ian Oeschger