I think, the question of the thread has been one of the most divisive during Amorims tenure. And it may very well continue since since some iterations of it, were part of the discussions since forever, very much so though with ETH and Ole.
During those discussions, I feel what happens a lot is mixing up terms like approach = system = formation. I don't think those are interchangable because they stand for different things.
@Adnan @sullydnl @MadDogg you are knowledgabe when it comes to tactics but I'd be happy to hear other peoples thoughts as well about a somewhat abstract topic - what comes first?
(edit: lets quickly define what I understand of the terms -
formation - the 3-4-3, 4-2-3-1 numbers thing, that gives a rough impression where players are expected to play,
approach - the "tone" of the game plan, aggressive, defensive, containing, pressing - so the style used to prevent the opponent to score, win the ball and create own chances to score,
system - a wide term that is for me the most highlevel idea when it comes to tactics for a specific match, covers formation, approach and lineup)
1) system follows formation
or
2) formation follows system
My understanding from reading and consuming content about football tactics is that the formation follows the approach. You decide how you want to play (pressing, containing, high block deep block mid block, look for space out wide, look for early crosses etc) then you look at what the opponent looks like and what his most likely game plan will be, then you look at the available players (your own and our opponents) and then you make a plan which player should cover which areas of the pitch to do x and y and which player of the opponents has to be taken care of and which of your own players is to be supported in case A or case B. The actual real formation in that specific game is something, that peels "itself" out of all those ideas (and to a degree also the ideas of the opponent) and from where each player is expected to start in phases on or off the ball.
It seems though, that many seem to think, that the formation comes first and then players get picked based on "what the formation requires". Can both be true depending on the manager?! Or is it either one or the other?