I've been tracking down an issue I've seen with the HTML5 publish in Captivate 2017. Through testing, I've discovered that the published folder is smallest/most optimized when the publish path does not include spaces in any of the folder names.
From what I can tell, the image files in the "dr" folder are better compressed and organized into fewer json files when published to a path with no spaces. For some of my movies, the overall size of the final published folder is cut in half. I have not changed any publish settings or other settings.
I do not know if this is true for Captivate 2019 or later.