3. Takes away the right to prohibit open carry, unless they follow state law.
Sorry for "mincing" words, but my comment is also tied into the "following state law" part.
No such thing as a "right to prohibit".
I realize what you mean, but you have also added "unless" which infers that the state does
have the "right" if it meets some unstated qualifier.
The state can only regulate. We give it the power to regulate. We posess rights which override this power.
There is nothing in state law that addresses open carry.
State law only regulates concealed carry. Therefore, pre-emption would remove the power of municipalities to regulate open carry unless
........nothing. It would remove the power of municipalities to regulate open carry period