I would recommend you to use Editable template to full fill your Iparsys behavior.
There are 3 things to keep in mind:
1. If we make changes to the "Structure/Content policy" that would get reflected on the pages that are using this template.
2. But,if any changes are made to "Initial content" then changes would not get reflected to already created page whereas if new page would be created, then that new page will have this new changes.
3. Any changes that we make on "Layout" would get reflected depending on the component that are part of Structure or Initial content that would get reflected on the pages accordingly.
So for headers/footer or any other components that you want to inherit, i would recommend you placing them in Structure mode.
Also, Iparsys doesn't work in template editor based pages.
-Kautuk