https://m.primal.net/HMGF.png
All within your client (no new NIPS / relay support needed)
1. From a post, have option to set "summaries only in feed" option for the follow..
2.  In "Feed" when a new note is found for respective person, display a summary message of posts and tags (see image mockup above for a summary of your mom's posts)
3. When use clicks "View now", all their posts since the last date you viewed "View now" are shown.
4. Update last View Now date for this follow.

I think this covers most of your use cases. 

 Forgot to add, clicking the # tag in the summary, only shows you their posts with that tag. I assume their are tags associated with product vs content posts, so you can view only the recommended product posts. 

 This is good, and wouldn't be hard to put together 🤔

Hilarious mockup btw 

 I found it hilarious you used your mom in the use case, so had to follow suit!