1) You can make even a single user instance have a wider reach through relays, especially targetted ones that are on the topics you're interested in. (More info at https://fedi.tips/using-relays-to-quickly-expand-a-servers-view-of-the-fediverse/)
2) Your own server's view of the Fediverse doesn't affect the visibility of your accounts to other people. For example my account @FediFollows has 60k followers despite being on a single user server with no relays.