Hello,
Please do not use dompdf 2 that was released after phpdocx 13 and it's not fully compatible. Use dompdf 1.2.2 or a previous version; or set the addHeadersAndFooters option as false.
The native conversion plugin supports a set of contents and styles detailed on https://www.phpdocx.com/documentation/conversion-plugin/preparing-the-templates-for-its-conversion (Supported OOXML tags and attributes when using the native method section).
The recommended conversion plugin is the one based on LibreOffice, that requires installing LibreOffice (https://www.phpdocx.com/documentation/conversion-plugin/conversion-plugin-installation-and-set-up), some shared hosting allow installing it, we recommend you contact them, or use a VPS (Amazon and Azure has free tiers for a whole year) or a dedicated server to install it.
Regards.