The first of these questions is completely a matter of personal opinion. The answer to the second depends largely on how one defines the word “effective.”
You can argue the first question either way. In fact you could even argue it three or possibly four ways. I could make plausible arguments that the US should not have fought either, that it should have fought in both, and that it should have fought in Korea but not in Vietnam.
To say that the US should have fought in both countries, you can say that, particularly at the time, it seemed necessary to fight in order to prevent the whole of Asia from becoming communist. When American leaders had to make the decisions to fight or not, it was plausible to think that communism was on the rise and that a communist Asia would be harmful to American interests. If communism dominated the mainland, the Philippines and Japan could fall and the US would have had no power west of Hawaii. Therefore, the US should have fought in these countries.
Conversely, you could say the US should not have fought in either war. You could say that neither was in our national interest. You could say that losing South Korea and South Vietnam would not have meant the loss of the Philippines or Japan. You could say that both Korea and Vietnam were far away and not very relevant to American interests.
Finally, you could argue that the US should have fought in Korea but not in Vietnam. Korea was a clear case of communist military aggression. When one country invades another, it is generally appropriate to help the victim of the invasion, particularly when it is your ally. In Vietnam, you could argue that the war started as an anti-colonial struggle by Vietnamese nationalists against their French colonial masters. There is much less of a moral case for war when you look at it like this.
As for the effectiveness of the policy of containment, let us look at two possible answers. On the one hand, we can say that containment was not effective. The point of containment was to prevent communism from spreading. During the time the US pursued this policy, communism did spread. Communism came to dominate, for example, Cuba and Vietnam during this time. Clearly, then, this policy did not work as it was supposed to. On the other hand, we can say that containment was effective because the point of containment was to prevent communism from coming to dominate the world. When we judge containment by this standard, it looks like a much better strategy. Containment was able to prevent the communists from taking over enough of the world to defeat the US. Instead, communism was contained long enough to allow it to collapse from its own inefficiencies and inadequacies.