Are out-of-state customers permitted to purchase any types of fireworks, even though that specific type may be banned in their home state ?

They do not restrict because, like alcohol, they leave it up to their patrons to make the correct choices for themselves

There are no restrictions on what you buy from here outside of what West Virginia permits.

Correct. They don't even ask where you're from unless you get a VIP card.

Yes. Anyone can purchase as long as you're of age.