A guest opens one link and lands in the space you invited them to. They see the four areas of that space — updates, files, approvals and activity — and nothing else. They cannot see your other clients, your team's internal notes, or which of your people are assigned to their work.
Guests never see anything about your agency's plan, seats or invoices.
A guest who is invited to more than one space sees a list and picks one. Most clients only ever have one.
There is no separate sign-up for guests. The invitation link signs them in, and after the first visit they can ask for a new link any time from the same address.