Hi,
The after_registration view file is shown to the user after the user signs up through the HikaShop user registration form page.
This page can be accessed by creating a menu item of the type HikaShop user registration via the Joomla menu manager.
The activate view file is shown to the user after the user validates the user registration form and the user account still requires validation through the click of a link sent to the email address address (there is a setting in the Joomla user manager options screen to turn on/off that capability).
When someone go through the registration form of HikaShop in the checkout, he can see the "activate" view file if the corresponding setting is activated, but he won't see the "after_registration" view file, since he will directly be able to proceed with his order.