Well it looks as if you got plenty of opinions regarding the salt, so how about an opinion regarding the mill.
I would recommend staying away from mills with pot metal grinding disks as the salt tends to cause these disks to rust.
I would also recommend avoiding the plastic grinders as they are intended to be used up and thrown away.
The best salt mill has ceramic disks. They are harder to find and you’ll pay a little more for them, but as the old saying goes... you get what you pay for.
mortar and pestle works okay for me