Not all plans include multi-user access. If your subscription plan does not have multi-user login then your invited users, regardless of access type, can only view the Dashboard and Alerting, but make no edits to the settings. They will however be available for assignment and alerting via Alert Policies.
The difference in Pingdom will be that these invited users are designated as BeepManager Users.
Multi-User access is possible, but a function locked to the Advanced plan and above.