Rundstedt approved of Mansteins suggestions. But the actual war plan was largely put together on OKW's initiative and by the OKH and its officers as the workers. Largely the decision to carry out an Ardennes attack and to draw the plans which are based on Manstein's suggestions was due to a series of war games which were organized. The German team won by a landslide and then every officer supported it. But the final plan was based on the Manstein Plan. I guess this speaks favorably of Rundstedt for recognizing that the original plans were insufficient. Rundstedt's real credit goes towards carrying out the final plan but it is worth considering that when the operations were actually carried out, French deployments prevented the Allies from actually doing anything about it.
I am assuming you are referring to the events after Sedan had already fallen? If I recall Rundstedt actually ordered all Panzer units to halt (and this is also around the events of Dunkirk). The plan was to take Sedan and move up the rivers towards the coast. I don't think Rundstedt was in support of their later actions, which were insubordinate. Rommel and Guderian are often glorified in the historiography but in my opinion it can be debated how necessary their independent actions really were.
ah, If you mean operationally then sure. Rundstedt did well enough at Kiev but in large part the success was due to orders issued from above. At the time Rundstedt was asking for immediate reinforcements and support. Something which Hitler was willing to do, but which went against the desires of people like Guderian, von Bock etc. Yet later Rundstedt seems to have joined the "attack Moscow" clique. In his memoires he also claims to have supported and strongly urged an attack on Moscow. His later performance on the Don was by no means exceptional. Was he correct about not being able to take Rostov? Yeah maybe. But I think above all his removal was actually about Hitler's desire to remove the more traditional Wehrmacht "Prussians" after the debacle of Operation Typhoon. Despite Rundstedt's nay saying the campaign in the Don was necessary and this is demonstrated by Stalin's fervent defense of the region simultaneous to Typhoon.
Minor side note but I always found it interesting that Rundstedt was given command of the main attack in 1939 and 1940 but in 1941 he was given the secondary Army Group South and von Bock was given the main thrust instead of playing support.