If importing directly into a bin, all formats regardless of size will be come the resolution of the project - in the case of Xpress Pro 5.1, you will be able to create 1920 x 1080 8 bit images.
If you want to refer to higher resolutions images and do a pan & scan of those sources (ala Ken Burns), then you need to use the pan & zoom effect. Once rendered, it will adhere to the project settings for SD or HD.
