Hello,
To generate a DOCX as a stream you need to enable the streamMode option (https://www.phpdocx.com/api-documentation/performance/zip-stream-docx-with-PHP). For example:
$docx = new CreateDocx();
CreateDocx::$streamMode = true;
$docx->addText($'Text mode.');
$docx->createDocx('output');
In this streamMode, when you call createDocx, the DOCX is generated as a stream, so after calling this method (createDocx) you can do anything you need with this stream.
If you enable $returnDocxStructure you are working with in-memory DOCX documents, not streams. An in-memory DOCX document is not a stream but an object that you can serialize or reuse instead of generating the file. On https://www.phpdocx.com/documentation/cookbook/in-memory-docx-documents you can read more information about working with in-memory DOCX documents
About using generateDOCXStructure, this method generates a DOCXStructure (this is an in-memory DOCX document) from a DOCX stream. This DOCXStructure is an in-memory DOCX document that can be used as template with CreateDocxFromTemplate and with other phpdocx methods.
Using phpdocx you can work with DOCX documents from the filesystem, as in-memory DOCX documents (https://www.phpdocx.com/documentation/cookbook/in-memory-docx-documents) or as streams (https://www.phpdocx.com/api-documentation/performance/zip-stream-docx-with-PHP).
We recommend you check the examples/Performance folder included in the Premium package that illustrate using generateDOCXStructure, parseDocx, returnDocxStructure and zipStream.
On https://www.phpdocx.com/en/forum/default/topic/2091 you can read a topic with the same stream question and how the user implemented it.
Regards.