No, Observers can only receive Mass Notifications and they cannot subscribe to Services.
Yes, they can view Service Status Pages which are set as ‘Public to the Organization’ from the Service Settings.
Observers have a pre-defined notification flow. They receive email and push (mobile app) notifications immediately when a mass notification is sent. If they do not have any registered mobile devices on their accounts, they would receive an SMS notification instead.
Yes, in order to send Mass Notifications, each Observer user needs to be added to your OpsGenie account and require a license. The license structure for Observers is different than regular Responder roles. Please contact our Customer Success team for further details.