Yes, if you're talking about blog posts, you can restrict access to a blog collection to only premium members. You can also restrict access to a specific forum (a set of topics), or a Resource set (a bunch of files).
You can also restrict access to any specific individual blog post, forum topic, or resource to paid-only members.
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .