From: Leeuwarden, Netherlands
About mixing units; definitely yes. Tanks are Inf killers but they can't take them all at once, so in gameterms that means put some Inf for protection (and scouting, tanks have a very low scouting value). But no more than the tanks can carry, I think that's five per tank. In gameterms it doesn't matter whether you put the Inf in a different unit or in the same unit as the tanks. But I prefer to make mixed units. So I have dedicated armoured units (with some Inf), Inf units with mortars, AT guns and the like, and mechanized units ( mostly Inf, some light tanks, armoured cars, AT guns, mortars and Mg 's ... quite expensive to produce, but real killers).
Flak low on supply can only shoot 1/10 or 2/10 of a turn... No more "ammo" so that's reasonably realistic.