To answer your first question, anyone who is a manager of the office can add/update and remove bookings. Some have opted to give their team leaders these permissions to allow them to do that, however, it is important to know that they’ll have admin access to the office too.
See this article for more information
As for your second question, Concierge will always start scheduling from
next week onwards. This means if you were to setup concierge for your team today (say 1 day a month on Mondays), then the first date should be Monday next week and the following date would be the Monday 4 weeks after that. Hope that makes sense - does that answer your question?