Hi @john_man - Thought I can share my experience on this, I could see on our AEP sandbox that adobe has used profile schema JSON with custom code method to transfer the profile related data to AEP with dynamic daya layer from web site. Ideally, they are sending all profile related information from web site for authenticated pages to AEP with profile JSON schema by utiliasing dynamic data layer to fecth the customer info and shared across to AEP. This is same profile schema that have been used on the datastream configuration.
Also as mentioned by @_manoj_kumar_ , there is an alternate way to send your profile data utilising HTTP API with same profile related schema with dynamic data layer to feed data into AEP.
Hope this will give you some light on your query.