Hey mate, I've solved this problem (frequency of updates) at Lenns.io. i.e. it's an opinionated RSS reader/tracker with a few unique features (at least they are unique when combined). You can tag each Feed Source into multiple categories. Then, you set priority weights (manuallY) to both Sources and Categories. That way - the sources or topics that you are most interested in always pop up at the top of your feed. Then, to avoid the issue with one source overtaking your feed - you can set a limit on how many posts you want displayed per feed.

I hope this makes sense. And, I will appreciate if you give it a go and share you feedback as an experienced RSS user. Cheers!