Membership In General Settings

Is is the same as following my site instead of blog ?

I do not know what you might be thinking is different there, but registration is about having an actual user account at the site…and that gives you the option of having a “members only” site (or certain “members only” pages) other people cannot read where a user account has a “Read” capability to get past that. And, that also gets registered users past your “User must be logged in to comment” option. But as to RSS “follows” and such, no, a registered user account is something different and not needed for that.