The Type 052C is a six ship class based on the original vessel, 170.
The Type 052D is a newer class, significantly upgraded over the Type 052C, with a different VLS system and more cells. A redesigned Bridge to accommodate a new and more powerful Phased Array Radar, a new, larger main gun, a reconfigured hanger space, a different CIWS fit, etc., etc.
So far, seven of the Type 052Ds have been launched, pennant numbers 172, 173, 174, 175, 117, 118, and 119. Of those, the first two are active and the third and perhaps fourth are on sea trials. The fifth and sixth are outfitting preparing for sea trails, and the seventh, which was launched in July, is continuing to fit out.
We know at least four more are planned (three of which are building)...and probably more.
All six of the Type 052Cs are active now.
We have seen those pictures of the "C" and "D" next to each other many times as they were building both classes at the same time.
Those pics really do amplify the differences.