Of these four types of languages, what is novel and deserves discussion is the possibility of languages where the nature of the direct and indirect feature checking movement differs, i.e., the languages where the direct WH-feature checking movement is overt while the indirect WH-feature checking movement is covert and the languages where the direct feature WH-checking movement is covert, while the indirect WH-feature checking movement is overt.
the predictions for these two types of languages is that a constituent can be pied-piped overtly by a WH-element which is not in the Spec on the surface (first type) and that WH-elements can appear in non-scopal positions without any overt scope markers (second type).