The limit does not apply to sub-forms (child forms). It only applies to parent forms and portals. You can add unlimited child forms.
The portal can have inside it an unlimited amount of forms, child forms, and tables. Those added functionalities don't affect your usage quota. It will still be counted only as one portal.
Editable shared view
Extensions that are set up with no login page (e.g. View Editor) are counted as a portal.