Permit access to all sites/users


I'm currently setting up a WordPress network and considering the types of users who will be engaging with it. I want to setup one group of users who can search/access all sites/users, without being manually added to any sites. So they essentially have SuperAdmin level rights in that area. But I don't want them to have access to any of the themes, plugins, settings or any other SuperAdmin stuff. They need free reign, but only in terms of viewing/searching/access users/sites.

What's the best way to achieve this?