1) The menu writer will make each "button" the same width for each layer of the menu. You can technically massage the code to define individual widths inline or have auto-sized widths in some cases but it can be difficult to get to work properly which is why it isn't supported natively.
2) You can control the css for each state in the wizard this includes setting and changing any attributes including background images, colors, or anything else.
3) Two menus can be used on the same page, or you can manually edit a menu to add an image inside. If you were to make a manual update you would have to repeat that update every time you updated the menu as it would be overwritten, wich may be the advantage of using two menus instead in that case.... of course the menus are easy enough to edit by hand using dreamweaver once created so personally I would probably update a single menu and commit to making future updates by hand as well once my design was generated.