Hello again,
I solved this issue and the solution turned out to be super easy. I simply prefixed the absolute server path to the filename parameter in createDocxAndDownload() and set the second parameter to true.
I actually disovered this solution while reading the documentation page for createDocx(), where the filename pararmeter description says, "The path to the resulting Word document."
https://www.phpdocx.com/api-documentation/layout-and-general/create-and-download-docx-with-PHP
However, the filename parameter description for createDocxAndDownload() says, "File name of the document to download."
https://www.phpdocx.com/api-documentation/layout-and-general/create-and-download-docx-with-PHP
This might be obvious to some, but I mistook this to mean the filename only and led me to believe the path is defined elsewhere (like in phpdocxconfig.ini).
I would suggest changing the filename description on the createDocxAndDownload documentation page.
In any event, thanks again for the support. I'm happy to put this issue to rest.