Since there are no official facts of how the game engine decides who wins and loses, all you will find here is controversing opinions of managers. I guess you are in a lvl 1 league otherwise your son's unmanaged team wouldn't be leading. As you go up the lvls and participate in more competions it needs more caring to keep up. As for formations, some managers stick with 1 while others adjust for every match to counter their opponent's. I belong to both categories tbh. I have 3 accounts that i switch formation every match and 2 that i keep same formation. All perform very well by either winning the league or placing at top 3 at worst.