The client activity notification module use 8 email templates and below are the names of the 8 email templates

Client Details Change Notification in general emails
Client Password Change Notification in general emails
Client Login Notification in general emails
Client Failed Login Attempt Notification in general emails
New Client Notification in admin emails
Client Password Change in admin emails
New Client Login Notification in admin emails
Client Failed Login Attempt in admin emails

To edit an of the email templates, go to Setup > Email Templates and click the edit icon next to the template.

You can also toggle plain text vs. HTML email sending on a per email basis from the editor page.