The new Item Preview Data Card gives you the ability to browse through a series of items with the next /previous controls, as well as to see the properties of a specific Item. The Show Map button on the data card gives you the ability to perform workflow actions instead of opening the Workflow actions tab. It also means you can perform workflow actions on a collection of items gathered from multiple workspaces without interrupting the flow of your work.
There is the potential to have quite a bit of data included on the data card based on the amount of fields that have been configured for the Item Details tab (The size of the card you referred to). The Data Card really gives you the ability to have a centralized look at an item as well as the ability to perform tasks in your business flow from the card.
The structure of the Data Card in not able to be changed but if you have a suggestion I would encourage that you post it to the PLM 360 Idea Station to potentially be implemented in a PLM 360 future release.
John Hill Support Specialist Product Support Autodesk, Inc.