RE: Portal Features : Custom Portal
Custom Portal does not contain all the features of the Community, Partner or Employee portal. It basically allows you to engage your customers and external audiences. It includes profile management, business components, web content publishing, and responsive design. Some of the other features such as blogs, forums, ideas, etc... might not be available with the custom portal.
You should be able to use the Dynamic 365 Customer Engagement data model to display information to customers, since this is part of the business components.
Hope this helps.