Some settings (properties) will safely ignore wrong values (e.g. ISO), others work with out-of-range values just fine (e.g. AFMA), and others cause permanent err70 (e.g. picture quality or video mode). There's no way to tell until you try it.
CFn's are just properties, with a higher chance of being camera-specific.
That's why I recommend to first check the valid values for any property, and only then try to change it.