Leased scan class understanding

I am setting up a new machine in our project. we traditionally create new scan classes for each machine and that is very useful for the driven scan classes.

However, I need some clarification for the Leased scan classes. The description is that it scans at the fast rate when any of the tags it contains are subscribed and visible in a client window.

Does that mean all tags with the same leased scan class will update at the fast rate, regardless of if they are subscribed and visible, when any one single tag is subscribed and visible?

Or

Does that mean only the tags that are subscribed and visible will update at the fast rate and the other tags in that class will remain on the slow rate until they are subscribed and visible?