I don't fully understand the differences between follower vs. users vs. subscribers.
- Jetpack Followers, also called Jetpack subscribers receive email notifications about each new blog post from your site. You can follow the instructions here to see your list of Jetpack subscribers. Readers have different ways to become Jetpack subscribers:
- They can use the Subscription widget in your sidebar (first option in your list).
- Whenever someone leaves a comment on your site, they can subscribe to your blog by checking the option " Notify me of new posts by email."
- A WordPress.com user can start following your site right from their WordPress.com home page, here: http://wordpress.com/#!/read/edit/
- Registered Users are people who used this form to register to your site. When they do so, they gain access to your site's dashboard, and will appear under Users > All Users in your dashboard. They will not receive notification emails when you publish a new post. If you do not offer any specific features to registered users, I would suggest that you disable registrations on your site, by going to Settings > General in your dashboard.
- Comment subscribers are people who chose to subscribe to a specific post; they will receive a notification email each time someone comments on that post. You can subscribe to a specific post by checking the "Notify me of follow-up comments by email." option when leaving a comment under a post.
Your site proposes one more Follow option (number 2 in your list), thanks to a plugin named "Follow". SInce you already use Jetpack, I would suggest that you remove this plugin, and use another plugin instead, named "Follow Button for Jetpack".