If you don't check the width scaling checkbox, then the responsiveness will not detect changes in your browser's (or device's) width. The advice I give on the 'Responsive Tips' section of the plugin's help page is that you never check the 'height' scale checkbox, but find a way to use 'width' scaling instead.
Here's what I recommend: Don't use the 'height' scale checkbox, but do use the 'width' scale checkbox (100%). Next, add your content to a group, and setup flexible layout properties on that group.
Or, you could make a narrow 'responsive layout' and a wide screen layout, so when someone makes their browser narrower than, say 700px, it will switch to the narrower layout.