If the goal is purely to weaken Germany, Morgenthau's plan is the most notorious by a long shot, but in terms of postwar realities it is likely to wind up looking like OTL.
Not entirely sure what Churchill's goal was, seeing as he recreates Austria-Hungary for some reason. But he was much more open to a united Germany than most of the allied leaders, so your assessment is probably correct.
Roosevelt's plan is probably the most viable IMO, and would still theoretically allow for a postwar European economic recovery while preventing the German dominance that certain powers so feared. In this situation German reunification is unlikely for a variety of reasons. It also calls for less ethnic cleansing in the east, and assuming that was honored by the Soviets/Poles that would probably be preferable. Long term there's a smaller Poland, and the political center of gravity in Europe shifts-probably to France. A less cohesive Europe is the likely result, unless I'm underestimating de Gaulle. Depending on who you are, thats either a good or a bad thing. No idea how it impacts the cold war, though the plan would probably make divided Berlin less likely-its simply less important in such an arrangement.