Tracking and assigning access gets confusing


I set up a WP Multi-site. Then I create a subdomain site with membership access levels. Then I created 4 fictitious users under the subdomain site.

How do I make sure that the blog posts which those 4 users create only are visible to members of the level where they are assigned? I used the user creator plugin. However, the users are not assigned to a subscription level yet.

I need to set up a fool proof system so that when a user signs up they can’t post content which is shown to the public or to a wrong subscription level.