When you add a person, you can choose whether this person receives an email with the login credentials. You can choose not to send this email, so you can use the person in the system, but that person cannot log in.
To show people with the same role you can use the dropdown menu on the right. Don't forget to select "All roles" again when you want to see all users. The table stores information like sorting, pagination, filters and searches in a cookie. If you refresh the page, the table will have the same filters applied. For instance, if you searched for a name, the next time you visit this page you will only see the results of this search until you empty the search box.
What is the green dot I sometimes see?
The green dot indicates that a user has been active in the system in the last 10 minutes. Not to be confused with the green dot next to the Manager role. The activity-dot is only displayed in the lower right side of an avatar.