Blurry Images and Story Size

Hi All, 

Like many others who have posted about this previously, I've been trying to fix a problem with images of documents and screenshots of program interfaces appearing blurry once I inserted them into my Storyline project. 

I followed the best practices guidelines and conducted dozen of experiments, trying out resized images, exporting doc as different image types (e.g. JPEG vs PNG) and using different resolutions (300, 600, 1200 pixels per inch), using the zoom feature vs. no zoom, and so on. Nothing worked.

I went back to the previous discussions about the topic and found a suggestion to try increasing my story size. It was set to 720 x 405, I increased it to 1600 x 900. That improved the blurriness of the offending images substantially. 

Here are my questions: what does increasing the story size do, exactly? What are the potential consequences of making that change (e.g. learners won't be able to view the content on smaller screens)? Are there any problems associated with increasing a project's story size after most of it has already been built?

Thanks in advance,

Katherine