@mike @andypiper @tchambers @shitpostalotl yep this is mostly correct via my experience on a single-user server. Following matters the most, but others’ boosts do cause those specific users and messages to be pulled in, so a nice side effect when looking at a user with no follow relationship is I can see the posts that my server got by whatever means, which means there was some activity I can go on.
Overall, fine-grained controls on federation, and especially controlling moderate proactive fetching of posts and content, is IMO one of the best opportunities to improve Mastodon.