Hello Seele,
I am sorry for the delay of this reply as it is a weekend for us here. Yes you can set some simple settings to allow only registered users to view and comment. Just follow these simple steps here:
1. You need to check in your backend > EasyBlog > ACL > Public and set the Comment to "No"
2. Go to backend > EasyBlog > Settings > Comments > General. Set the non-members to cannot view and cannot post
Hope this helped. Thank you and have a great weekend
Regards,
Apson Chom