When importing customers from cPanel by default they aren't assigned to any 'Customer' or 'Package', we just went through after and created the Customers and assigned the Packages.
If you don't assign a Customer/Package to a website you are correct, there are no package restrictions or limitations.
It would be advisable to create a Customer and assign a Package even for your own websites, unless you have those websites assigned to individual cloud servers where you want to allow them to have access to all of the available resources. Just keep in mind if you want to enforce Disk Quota you will have to go to 'Servers >> Application settings >> Web server >> Website disk quota' and enable that, and 'Bandwidth' on your packages is not a hard limit, customers will be allowed to exceed package limits for that. It will turn red but won't suspend them or do anything about it. In the next few months there are supposed to be some improvements to this, including allowing more 'Overrides' to package settings for specific subscriptions which will be a welcome addition.
