In a duplicate game today, my partner and I set our non-vulnerable opponents two for a score of +100. We got a bottom because other pairs with our cards earned part scores of 140. On the other hand, we would have earned a top if "down two" meant +200.This could come about if the opponents were vulnerable. And of course, down two doubled, non-vulnerable would be +300.
Is this result peculiar to the one game, or do good players follow a pattern of doubling in these types of situations when the opponents are non-vulnerable, while refraining from doing so when they are vulnerable. (The danger is that doubling may help the opponents make the contract or go down less.)
Also, would good duplicate players be more inclined to double non vulnerable opponents when the opposing contract was two of a major (+110) rather than two of a minor (+90)? (Rubber bridge players would be less inclined to double two of a major because of the risk of doubling the opponents into game)