Recently I have encountered a situation where I got a few good heroes of the same colour but did not think ahead to train the troops. So I have one troop team which is quite good and then a lot of one star and two star troops. While testing the team made entirely of the same colour I have noticed that sometimes tiles turn into strong troops, sometimes into weak troops. The strong ones do more damage but I cannot find any correlation whatsoever on what determines which troops the tiles turn into. I did my best to search anything written on the topic but found nothing except the basic guides. Is it possible to control or predict which troops the tiles turn into when joined?
Any help on this topic will be greatly appreciated. And please feel free to correct me on anything.