A somewhat unconventional UI for following content, which incidentally works with RSS Box, is Fraidycat[0]. It groups recent posts under “individuals” with a visualization of how much recent activity there is in a given feed, and allows to choose “follow intensity” which works in a nice and transparent way.
https://fraidyc.at/
It's a browser extension, and it's been very pleasant to use. I came across it on a previous Show HN post: https://news.ycombinator.com/item?id=22545878
Now if only it worked on mobile…