Crystal Clear III contains Dynamic Contrast and SCAVEM. Dynamic Contrast stretches bright and dark shades to increase contrast, and SCAVEM attempts to make bright images look sharper by adding bevels around the edges.
There is a version called Digital Crystal Clear, which adds an analog comb filter and an analog luminance transient processor ( LTP). The LTP is digital though in the Pixel Plus sets.
Crystal Clear III does not include a comb filter, although some Philips leaflets erroneously state the opposite. In some of the 100Hz sets though, the digital processing suppresses cross-color artifacts a bit. The resolution is not improved by this processing.
However, in actual moving footage I don't think there is a major difference in performance with and without comb filters on Philips 100Hz sets (on my set regular off-air TV actually gets a little sharper when I turn the comb filter off in the demo menu).
With S-video input a comb filter would be bypassed, so the absence of it in Crystal Clear III does not impair performance so long as you use S-video for your S-VHS VCR. Being a S-VHS VCR it might well have a comb filter itself, improving signal separation before recording.