I've noticed that DW seems to impose its own image sizing to images in posts (example: I wanted the width of the images on this post to be 80%, and they are clearly not. Clicking on them gives me the full size image, which I don't want, either.)

So:
(a) what are the default resizes? Is it to a specific pixel height or width?
(b) is there any way I can change it on my end so that my images show up as a % of container width instead of being forced to be too small?