Here's an overview of what users can do depending on the role they have:

Action Superuser Owner Masked Role
Create the extension Yes
Drop the extension Yes
Init the extension Yes
Reset the extension Yes
Configure the extension Yes Yes
Start dynamic masking Yes Yes
Stop dynamic masking Yes Yes
Create a table Yes Yes
Declare a masking rule Yes Yes
Insert, delete, update a row Yes Yes
Static Masking Yes Yes
Select the real data Yes Yes
Regular Dump Yes Yes
Select the masked data Yes Yes Yes
Anonymous Dump Yes Yes Yes

Security context of the functions

Most of the functions of this extension are declared with the SECURITY INVOKER tag. This means that these functions are executed with the privileges of the user that calls them. This is an important restriction.

This extension contains another few functions declared with the tag SECURITY DEFINER.