Tideline checks every feed every 15 minutes while it’s open, whenever you come back to it, and when you pull to refresh. Pulling to refresh always skips the server copy. Reddit feeds are checked one at a time, 30 seconds apart, a little after the rest, because that’s all Reddit allows.
Hide kinds of stories everywhere, and fold the same story from several sources into one. Switch any of these off to see everything again. Your choices sync to your other devices.