Disabling proofing helps. Track changes was off, I'll do some more digging to see what else I can disable.

I was hoping that there is a tool somewhere that removes all xml tags that are not needed for the content of formatting.

To clarify, I am using phpdocx to take a docx template, replace lots of variables defined in the template for text and then save it as a PDF document. Replacing variables takes seconds to process because the xml document has all these weird tags in between. Without those tags, phpdocx would just need milliseconds.