If you make someone a Form Administrator, they only have control over anything related to the particular form (or forms) to which you give them access.
They'll be able to see and download reports and statements, but they'll only be able to see data for the forms they can access. They can also make changes to those forms and their receipts, view and edit recurring payments, create events, manage receipts, and manage social media settings, as well as enter donations and registrations in the Virtual Terminal.
If someone is an Account Administrator, this means they have control over everything involving your Qgiv account. They have all of the permissions that Form Administrators do, but they automatically have that control over ALL forms on your Qgiv account.
In addition to those capabilities, they can manage Donor Accounts, create/edit widgets, create/edit API tokens, add/remove users and set permissions levels, add and edit notification recipients, send out Donor Summaries, configure third-party service integrations, update your organization's information, and clone forms in the My Qgiv area.
You can read more about configuring permissions here!