If you are seeing plugins menu items like that, you need to tell the plugin developer that only Administrators should see them, and not all other user roles. That’s an error in their plugins, not WC Vendors related…….
And as for editing the new/edit product page, you can’t — you need to use WC Vendors Pro instead if you want to customize it since with Pro everything is handled from the upgraded dashboard on the front end. 🙂