I think you are confusing the standard Vendor Plans addon with the new Vendor addon (not sure of the name) that adds additional functionality but comes with a hefty price tag. Not familiar with any Vendor Tabs addon from cs-cart. Must be from 3rd party.
Yes, you are right. The new is Vendor Privileges. Mea culpa. As for the other, I said it's "fourth-party"
This is the Vendor Privileges metrics_multivendor.post.php
$schema['vendor_privileges'] = true;