Yes, banners can be different sizes, but that's not recommended because it will make the content below "jump" up and down as the slides change.

The slideshow is as large as it's parent container. That means if you put it in a container that is full screen width, it will be full screen width. If you put it in a container that is 500px wide, then the slideshow will automatically adapt to 500px.

Don't get me wrong, but please try reading the support thread - all of these questions have been answered already. Including instructions on how to do it...