The containers around the images or sliders can be adjusted by the theme options under the Header Image tab in the customizer. This will control the spacing (paddings). The height is based on what image or slider height you use…so if your image is 600px in height, the showcase or banner area will adjust to it automatically. For sliders, they usually have a height setting which does the same.
Max-width means that is as wide as the container area will go. So whatever these are set, that will be the maximum width.