Hi
The kernel size can be thought of as the number of pixels down the line you are looking along that the edge must occur over. If you have a crisp clear edge (goes white(255) to black(0) in 1 pixel) then you can have a kernel size of one. This will never happen in real life as the image edge boundary will never line up with the pixel boundary in the camera and lighting will also play a part. Increase this if the edge takes several pixels for the change to happen.
Projection width is the number of lines that you are looking along. If you have an imperfect edge, maybe a stamped part, then this will need to be larger to cope with the irregularities in the edge. Do not make this too big as if the lines you look along are not perpendicular to the edge you are finding this will return different positions and confuse your edge.
Unfortunately there are no ideal values to pick as this is entirely dependent on lighting, optics and the part you are looking at. Hopefully my comments will make it easier for you to understand what effects these settings will have on your application
Mike
