I've only ever known one properly adjustable salt [or pepper] mill.
Most of them just work on how tight you fasten the knob on the top.
For the past 25 years or so , I've had one made by William Bounds, a US company, though I got mine straight out of a UK department store.
The knob doesn't dictate the grind, there's a dial on the side, Coarse, Medium, Fine. Looking at their web site - which looks like something from the early 90s & is a nightmare to navigate - they seem to do ones with 5 levels of adjustment now.
I have no way of knowing whether you'd consider the 'Fine' fine enough. I use mine on coarse, for that crackly top presentation.
Here's a link to how their mechanism works
Just to note that, though I have a pair of these, I don't use the other one for pepper, I don't think it's particularly great at that; it's not fast enough for me - though I see they now make a high-output 'pro' mechanism [bottom of the linked page] which I'd be tempted to try.
I also must add that I don't spend a lot of my time researching salt & pepper mills - so there may be many things out there that have completely eluded me over the years.