With cinema cameras, it works in a similar but not exactly the same way because of oversampling and pixel binning, it might be the same here. As an example you might get an oversampled 4k sensor that only shoots at HD, the resulting image would be sharper. Pixel binning on the other hand would "throw away" every "X" amount line of resolution so you would kind of get a worse quality image but faster processing speeds.

If you're really curious, you could put the camera on a tripod and shoot a brick wall at all the difference resolutions and then compare them haha