white:this lets you manually overwrite the clipping point. ideally    everything would be normalised to clip at 1.0.
desat:controls the amount of desaturation of highlights. it is a parameter  because there are cases for both extremes. some images come with chromatic  aberration artifacts near clipped highlights and would thus only blur false  colour magenta into the clipped region. you want to desaturate this  completely. however, things such as saturated skin colours should be  inpainted with the original skin tone, i.e. not be desaturated at all.
soft:controls the amount of *softness* of the inpainting. essentially this weighs  different scales of the wavelet pyramid. no softness means the highest frequencies  get a good share of the result. all soft means pretty much only the coarsest scale, i.e  close to constant colour reconstruction. again, when inpainting chromatic aberration artifacts  you may choose to go soft, but when reconstructing a smooth gradient of a sunset you want  a specific kind of gradient.
