dont thinks its a must. i am using same tactics and also tried the difference between long and mixed passing and i didnt realize much changes. but always use passing down flanks since the most ppl in the game are going for central formations. i also realized that my mc's dmc's and amc's have not as good ratings as my wing players or strikers in general. idk if this is normal but i have the feeling that it is better to not use too much players in the middle.