Question
Is there a way to disable or restrict the Nintex Workflow/Forms apps from getting activated in Groups and Teams?
Answer
Currently SharePoint Online apps can be added to a Group site by any member that is within a Group site's Owners group. This level of permissions is also applied to the Nintex Workflow and Nintex Forms apps for Office 365.
Additional Information
There is a feature request for higher restrictions on the apps within the new Group Site site type here, and if you would like to raise the visibility of that request to the product team, please add a vote to the request.