Given that there are governmental departments for interacting with muggles, and qualifications taught at Hogwarts, my assumption was that it was like many other fields of study typical members of the public did know little, but plenty of research exists. How much does the typical person know about nuclear thermodynamics? Not much, and they don't really need to, but that doesn't mean all of humanity knows nothing. Hermione states pretty regularly that the spells protecting Hogwarts protect it from being discovered and prevent electrical communications from functioning.

I would think that, in a war with muggles, any wizard signing up to fight would be given training (by those few governmental and academic experts) in muggle warfare, weaponry, and relevant defensive spells needed for such a conflict.