Confluence allows you to configure groups and individual users just about anyway you like at the space level. However, the "Restrict View" and "Restrict Edit" options at the page level are, well, too restrictive.
You can only select 1 user or group for page level access. This forces the creation of "artificial" groups. For example, I have a group for my developers wilth r/w access to a space and a group for my client with read access to the same space. We've a situation where 1 individual in the client organization needs r/w access to a few pages in the aforementioned space. It appears that the only way to accomplish this is to create a new group (my developers + the one individual).
This is further exacerbaed by the user/group handling. There's no way to 'copy' an existing group to a new one,si