I have a number of playlists that show like: Top, Coming Soon, Out Now. And under each is a list of image thumbnails with titles to play a video. They are linked to each category like so:
So the "topfilms" tag gets it placed in Top. The home is now using a lot of bandwidth loading all the hi res thumbnails, so was seeing if possible to create a sub category under neath the three main, that opens another set of categorized tags as it were.
At this point, I think it would benefit you to read the JSON spec to get a better understanding. The spec does contain some samples of feed objects. You should also consider not coding your feed manually.
Windows desktop software for creating and managing MRSS, JSON, and FireTV feeds @ https://github.com/rrirower. No Programming, JSON or MRSS knowledge required.