These aren't directly editable in page as you've noted.
So the question is what determines the layout and sizes of these prebuilt items?
If you lok at the xml file 1.xml then you'll find a block named design content.
This is a seies of htl code lines squished into a big block, and inside of that there is a table structure tr td tags. This is where you can change the block to whatever you want it to be.
The caveat being it needs to be done sfter the module has been mastered for the media of your choice or it will revert.
It's a shame that an external css page isn't used for this as it would be easier to modify.