No that is a variable you must add to sowgb.ini by hand. There is no difference in AI performance at the normal or historic levels. At the veteran level the AI is more aggressive, but not any smarter.I'm not sure what you mean by aicount. Is the diff harder on veteran or historical?
The AI will at times send it's forces in piecemeal, just as some human commanders did. At other times it will hit you with the entire force at once, again just as some human commanders did. The hallmark of this AI is that you can never predict how it will act.