This module allows users to manage notification emails with the Mail_Edit module. The notifications module uses message template classes that must be edited in code.
Administer permissions allows assigning all permissions to any role, even to the anonymous user role! Specifically, a user with this permissions can obtain any other permission for himself.
Administer users allows editing any user, including his own and even user 1. This includes
assigning/removing any roles (and thus any permissions),
changing the user's name (to cover his tracks),
changing the user's password (to downright hijack an account), or
changing the email address (to obtain a log-in link to gain access to the other user's powers without his knowledge).
It also allows deleting any user, including user 1, which can seriously disrupt the site's operation.
This means that either of these permissions allows obtaining complete control over your site, and you as site administrator or consultant may be reluctant to give a role with either of these permissions to someone else, because
you may not trust their Drupal competence,
you may not trust their integrity, and/or
you may not trust their ability to keep their account safe from others.