#1 depends on the sensor in the camera. based on google search for the sony IMX183, it looks to me like it's GBRG, or GRBG. if your input files are fits files, then due to an ambiguity in the fits spec, it could be either pattern depending on what direction the fits file was written out in. the easiest thing to do is to try to take a picture of a terrestrial scene for which you know the colors, then load and debayer the image and see if it looks right.
#2 is entirely up to you. superpixel debayering makes an image that's 1/2 the size of the sensor in each dimension; it does not try to interpolate pixels but instead just puts all the red pixels next to one another, all the blues next to one another, and averages the two greens and puts the result next together. the other methods are different variants of interpolation, where the software "makes up" a red value for each blue pixel and green pixel, a blue value for each green and red pixel, etc. so that the resultant image is the same size as the sensor.
rob