Questions about invoicing and free period


Have some questions about WHMCS and pro sites. Is it possible to use WHMCS for ordering, billing and management of customers, then use the pro sites for handling different packages? For example, what plugins are included in the various packages and more.

Then I wonder if there is any possibility to manage the free period in WHMCS without any invoice is generated? I would like the customers to test for 30 days and if they are satisfied then they can order the package they want and only then will they get a bill.