selecting another village to watch would be the same thing as quitting i imagine since the game is not actively running so everything done would be based on calculation. From my experience minimizing the game is like hitting pause if i remember (dont quote me i forgot my laptop today) the villagers dont move when its minimized. Game running in the background is the same as running in the foreground cept no noises. Fastest is having the game off because there is no slacking on the villagers part, its all based on numbers at that point.