Pruvan APIv2 Internal is the same as Pruvan APIv2 External as far as setup.
Your work provider will tell you in you need to use Pruvan APIv2 Internal or External. If there is a question, ask your work provider what Pruvan APIv2 Integration (External or Internal) is required.
The difference between Internal and External integrations to Pruvan is based how the Order Source controls the related Pruvan account.
About Internal vs. External integration types for integrated accounts
Internal integrations allow the Order Source to "DIRECTLY" administer the linked "internal" Pruvan account. Typically there is only one Pruvan account directly linked to the Order Source when an Internal integration is used. Internal integrations are typically aware of all Pruvan sub-user(s) in the linked Pruvan account and may directly set and update sub assignment in the linked account (assignedTo), and directly control and update the status of all related order fields. The Auto-Admin feature is always "ON" for the linked internally integrated Pruvan account, meaning the Order Source can auto-administer all linked Pruvan accounts.
External integrations are typically made to numerous "external" Pruvan accounts. The Order Source may initially set (on order creation) all order fields. External integrations cannot directly update the related Auto-Admin fields if the Pruvan account holder has Auto-Admin turned "OFF", allowing account holders to change these fields without the Order Source overwriting changes.
External integrations typically have no knowledge of the Pruvan account sub-usernames for sub-assignment. External integrations can technically set the assignedTo field if a proper sub-username is provided in the order feed but this is not recommended.
See Auto-Admin option for details.