Please check Nik 7 Color Efex - Gloabl Adjustment filter - control points ... question.
Post #4 explains the different handling of Viveza (= single filter) and Color Efex (= container for several single filters).
One more thing: In ColorEfex you can drag a single filter to a different position in the stack. This changes the effect of the filter in a similar way to a pixel editor with layers.