How many workspaces your plan includes

Why unlimited only at the top

On Agency Plus the binding limit is already your tracked capacity, so uncapping the workspace count gives nothing away. Lower down, the workspace count is the thing that makes an agency move up a tier, so uncapping it there would remove the reason the ladder exists.

What happens when you reach the limit

The New workspace button tells you, and points at the plan that fits. Nothing you already have is affected.

Workspaces and capacity are separate limits

Having five workspaces available does not mean five times the capacity. Capacity is one pot for the account, and five quiet workspaces can sit inside a Business plan comfortably while two demanding ones might not. The Capacity page shows the split before it becomes a problem.