The correct answer is A. Make the Opportunity Type a required field on the initial Opportunity page layout and use automation to update the record type based on the Opportunity Type.

The requirement has two phases: first, show users only the fields needed to create the Opportunity; after save, show the full record page based on the Opportunity type. This can be handled by using a required Opportunity Type field first, then automation can update the Opportunity record type. Salesforce page layouts can be assigned by profile and record type, which allows different Opportunity types to show different layouts after the record type is set.

B is incomplete because it only mentions page layouts based on profile, not dynamically changing the layout based on Opportunity Type after creation. C is incorrect because sharing rules control record access, not field display. D relies on users manually expanding sections and does not meet the streamlined requirement.