If I understand correctly, we could just link pictures at their highest resolution and DDF will automatically resize it to fill the width of the screen. Is that correct?
Yes, but that's probably not a very good idea.
It'll make the pages load a lot slower and kill a ton of bandwidth and memory unnecessarily.
Although in this case it's not "our" bandwidth we're concerned with, unless your on a cellphone with limited data...
5 years ago that would've been acceptable. the trend these days (and for a good reason) is "mobile first."
The "smart" way of doing it would be to either have the default be a small image and use javascript to have it load a bigger image as appropriate, or to use CSS media queries to load an appropriately sized image (as a background image) to begin with.