Well the main doctrine you should use is Grand Batle plan for offense and Supeior firepower for defensive.
For inf you should go for the one that reduces the width,for support you go for engeneers path and in tanks you can choose Tank destroyers are the meta so go for that if you don´t want to think much,and for the last part i think you should go for the one who gives you the most battle planning percentage.
Also for arty you still can use it as a support company is still prety good in general,just don´t use Line artillery,still not worth it even after the changes.
And the support companies should be field hospitals,supplies,anti air,Signals and the 5 one is what you like really or go meta and use artillery.
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