The user you’re using to take this screenshot has enabled “show hidden documents” which is why he’s seeing a lot of content that is hidden. By default all users created don’t see hidden documents so this means an explicit action was done to ask to see hidden docs.
Yes ofc it’s possible to restrict anything using permissions but:
- Beware that some internal pages (especially in the XWiki space) need to have view access for everyone or some wiki features won’t work
- You can set the permissions in the Admin UI, for the whole wiki and per page. See doc https://www.xwiki.org/xwiki/bin/view/Documentation/AdminGuide/Access%20Rights/