By default, WHMCS does not have any kind of restriction on user registration. That is, without email verification a customer is able to perform all tasks. But using Email Verification Extended your customer won't be able to perform any tasks.

========================= ADMIN FEATURES =========================

• Enable/Disable Addon.
• Can view as Simple Pagination or Bootstrap Based data in module page.

========================= REQUIREMENTS =========================

• WHMCS Version 8.x or higher
• Module License Key