Set more than 1 module image size

Hello,
I see in the themes -> default -> blog images area I can set the image size for modules. I'd like to set 1 size image for the sidebar position and then a larger size image in the template areas below the mainbody area and above the footer area. Can you please explain to me how to assign a different size image to modules located in a different area of my template?

Also, in the module for "most popular post", there are image and video settings. What do these settings apply to since they do not override the settings located in the theme area as shown above.?

Thanks.