Using the same formation (if it's a balanced one), or searching for a counter to your opponent ?
Both can work (of course setting different orders/arrows, the team changing a lot).
There is not the "one" right way to play.
In my 13th season, I had won all the leagues, the CH.L. and 4 trebles.
When I started playing the game and till lv3, as I had a better team than most of my opponents (5* and 6* players), I was setting attack mod.
After I became a forum member here (at lv2) and start reading many posts, I switched my mentality to defense/counter and tried to find counter formations, so you can see the analogy of goals (GA - GF). I still playing defense/counter in 80-90% of my games.

At a complete loss as to what happened...-overview-history.jpg