You are correct that Subforms/subreports are called "Portals"in FileMaker.
You can't, however, put a portal inside another portal though you can use portals in a list view--which you can't do in Access so each system has its strengths and weaknesses.
You can resize the rows of a portal to any size you need and specify any number of rows for display. Thus, you can get a form view style portal by resizing the portal row to make it taller and specifying only one portal row.
Also keep in mind that you can place fields from related tables inside a given portal. Thus, you may be able to make a portal to Acts that includes fields from Shows. Other times you can use a script synchronized "detail" portal next to another portal. Selecting a record in the first portal triggers a script that pulls up related records in the detail portal.