Hi,
Assigning PFCG role to user on Portal -> This approach is used mostly in EHP7. Was available earlier as well but from EHP7 this is the only option to access roles in portal
Assign standard portal role to user (content provided by SAP in portal content seection). -> Till EHP 6 the role structure was different. You could deploy business packages and assign those role to user in portal. No need for role upload from backend (PFCG).
In both these cases, If you are using enterprise portal, you need to assign roles to end user. Role could be obtained either by deploying business package or by role upload from backend.
There is no hard and fast rule that to hide links you need to use PFCG /LPD_CUST. It completely depends upon the role that you are using. If your role has application that is pointing to LPD_CUST (example : HRESS_A_MENU) then to make applications work you need to use LPD_CUST. So usually in those role you will have minimal iviews and that will point to LPD_CUST which has all the other applications.
Attached is screenshot of ESS role in EHP6 which has only one iview "overview" which points to LPD_CUST. Rest of the iviews are OBN based iview which is called in runtime. In this case , you need to use LPD_CUST and change the visibility of application links.
But the roles that you have uploaded for WDA based EHP7 , to check whether it points to LPD_CUST, you can figure that out from the application name present in iview in role.
Hope this helps.
Regards,
Navya