I'd start with setting the combined frecency score to 0 and testing out how the raw fuzzy scoring does. Then if you find you're having trouble finding recent or frequent commands, you can adjust from there. If you can't find a configuration that feels good, please feel free let me know in an issue.
A viewer and editor, but essentially yes — the Hub handles sharing and collaboration for you, as well as realtime collaborative editing and a few other features (and likely a few more to come). We want the Hub to feel like the most frictionless way to collaborate on runbooks, but we understand that some folks don't want host their runbooks with a third party, and sometimes fitting into an existing VCS workflow makes the most sense.
The backend server, Atuin Hub (https://hub.atuin.sh), isn't currently open source, but the open source desktop app can still connect to it. We also support offline workspaces if you prefer using Git or another VCS to manage and collaborate on runbooks, rather than using Atuin Hub.