Back on Google+ a "views per follower" (VPF) metric was in vogue for a while, see:
https://globerunner.com/introducing-new-google-plus-quality-...A few things stood out:
- VPF was typically low. Ghost town...
- High-follower counts typically had low VPFs, lower-but-modest follower counts: higher. This follows from an attention basis: low follower counts tend to be more directly engaged.
- Actual values were all over the map, and informal sampling tends to be highly biased.
- Useful sampling probably starts with at least both of most-heavily-viewed channels and most-heavily-subscribed channels. Those are the ones which are succeeding by at least some metric. You'd likely also want to include most-viewed videos, though one-hit-wonders can also distort results. (Tom Scott's observation that you don't want instant success, but more of a slow burn, is very apt.)
Again, from G+, here looking at Communities, what I found was that it was not the total number of members that mattered most, but the rate of new content -- and no, more isn't always better, but none is fatal.
Looking at visible metrics (community name, subscribers, visible recent comments, plus-ones ("likes"), and re-shares, correlation was highest with more posting activity, at least to a point (based on the visible rate of new posts).
Large groups with no posts => no activity.
Small groups with relatively frequent posts, often => high activity.
After a point, size seemed to count against communities (~10k members or so).
This is based on a comprehensive dataset of summary data from all 8 million G+ communities, provided me by Friends+Me during the G+ shutdown. See:
https://social.antefriguserat.de/index.php/Migrating_Google%...
Also:
Activity crossplots:
https://joindiaspora.com/posts/13680950
Membership distribution (log-log):
https://joindiaspora.com/posts/13738258