Hello,
UPDATE: Premium licenses include the stylesReplacementType option to use the placeholder styles when doing replacements by HTML.
You can get all information about styles,using getWordStyles, available since phpdocx 9 (https://www.phpdocx.com/news/post/phpdocx-v9-release-notes/218).
For example, using this method you can get the font size used in a content or style (default, custom and others) from a template or a DOCX generated from scratch and use it to set font size values with HTML, addText and other methods.
Regards.