You're not doing anything wrong. The Resizable option is only applicable to Search cards. All of the others can't resize. Unforutnaley, you'll need to either change resolution on laptops (not likely) or change the shape of your Template card.
This is a bummer. Doesn't seem like there could be a big technical hurdle to changing this... In one sense it makes card creation easier, because it gives us fewer options.
At the least they could hide the "Resizable" checkbox for cards types that it does not work on!
I agree with the others, you will have to change the size and shape in the card editor, and then test it on those machines where it appears large.