Hello,
Yes, when you call createDocx, it creates a DOCX; this is how phpdocx generates and saves the documents (that's not a temp file but a final file you can storage, download...).
If your script generates more than one DOCX in the same path with the same name, then you need to set unique file names to avoid overwritting the DOCX outputs.
You can set unique file names with any phpdocx license or with the Premium license you can use the in-memory approach to don't generate files in the file system.
Regards.