[Imp]

Wow big ask Roman & depends what you want or can afford stand of weapons or standard etc. For WWII generaly cannon vs armour MGs vs soft then look at secondary weapons.
Do same as for any other unit look at weapon stats kill for infantry AP or HEAT for armour.
Important planes only ever have HE ammo so do not use HEAT rating use AP one. Helicopters do use HEAT rating if have ammo for listed under AP.
At least thats the principle I work on.