How do I block or disable regular users to access certain areas in Security and Compliance?

Actually they should be able to see their quarantine, that's the location from where they are supposed to access it now. The Service assurance group is just a bunch of links to documents and the compliance manager, no harm there. Records management does seem like an oversight, it should not be visible, but it doesn't expose any sensitive information anyway.

As for searching other users, that's no different from using say Outlook. You can see the same details there, including the roles of a user. No sensitive information is exposed, such as activity or alerts.