If you want to restrict sub user access to form submission data, then you must assign a data view to that sub user.
First you create a Data View, then you can assign that data view to a sub user as their primary and perhaps only view of the data. With a data view, you can restrict what types of records and columns are available in the Data Access Module which provides a special type of restricted access. For example, you might create a data view with a filter that displays records where the value of a SalesRep field is "John", and then assign that data view to a sub user account for John.
You can assign multiple views to a sub user, and they can switch between them. However, if you want the sub user to have access through only one view, then you must choose that view only.