It just depends on your style and opposing formation and quality ratings etc.

There are is a lot of good info in this forum, that you could read upon. And there are the veterans like dv8r etc that have been playing this game for a long time.

I tend to adjust my formation, countering the opposing team, but that's just me. Itnworks well for me, other use the same formation all the time and it works well for them.

Spend some more time in this forum.