@Ed
Those are a secret-handshake / TCP connections, for gossiping SSB data (exchanging messages and blobs).

I don't know how many people usually unfollow pubs, but it is fine to do so, as long as you still follow at least one feed in the network. (Some people have unfollowed all feeds and then wondered why their network seemed dead). The main reason to keep followings pub I think would be if you want to discover new-people who arrive via those pubs.

Additional threads:

• %YOTIrEz... When to unfollow pubs
• %ZxOfmnj.... About following/unfollowing pubs
• %4nder6u... "Should I unfollow some pubs?"
• %NIQ/MeW... What happens when pubs are unfollowed
• %WbiJktX... How connected pubs came to connect
• %M39Tsrl... "what does a "connected pub" mean?"
• %jCccOik... What is happening with connected pubs
• %oNCXoPV... What are connected pubs
• %TrSbcVg... How can I disconnect from a Pub?
• %mVyrqCo... Following vs. joining a pub
• %dVA3rQP... "Is it time to stop following Pubs and following only Users?"