The first two are to start backtrack with framebuffer modes (rendering to console, refer to google) with specific resolutions. Some monitors can take 1024x768 but for backwards compatibility, there's 800x600.
Those first two options are the ones you should be concerned about.
If you're going to run it off via unetbootin, you are stuck with only one partition for hosting BT4 image. That doesn't mean you can't create another partition on the USB stick, but you can't simply move the BT4 image around and expect it to work. Other than that I don't know what are you trying to get at with saying about partiitons.
There are guides and howtos on creating a persistant BT4 setup on USB sticks. I suggest you check out the BackTrack 4 Howto section.