Main Options Step Size controls the amount, or strength of the filter. The value you set here affects the image for every iteration, or warp step you make. Iterations sets the number of times the filter should repeat the effect. Secondary Options Dither Size causes pixels to displace randomly, thus decomposing the image. A moderate dither size just makes the warp curls look more grainy.
Larger values scale from fuzzy particle clouds to total disintegration of the image.
90 degree rotation, which is the default setting, makes them look like small whirlpools. A 0 degree rotation looks more like the kind of solid distortion you'd see through a bathroom window. Every other angle are combinations of these two, more or less so depending on how close they are. Substeps increases calculation time for each flow step. There is a slight improvement in warping, but it is much slower.