Hello,
Yes, you need to create a WordFragment with an image and then add the WordFragment to the cell table.
Please check and run the example Core/addTable/sample_2.php available in the package you are using. The XML you post is the internal OOXML image content, files are added in the word/media folder of the DOCX.
The streamMode option is available since the release of phpdocx 7.5 (https://www.phpdocx.com/news/post/phpdocx-v7-5-release-notes/213).
Regards.