The support to transform HTML to DOCX is really good, and almost all tags and styles that have equivalence in Word are supported; of course you need to follow some good practices to get the best output.
We recommend you to read the documentation available on:
to understand how to import HTML and get the best output.
About conversion plugin, there's no trial of Advanced or Premium packages, only the Basic license has a trial.
If you send to contact[at]phpdocx.com two or three DOCX samples we'll send them back transformed to PDF and RTF using the conversion so you can check the output quality.