The salary question is simple to resolve:

list the salary range in the advert.

Everybody should know, before they are ever asked their expectations, what the range is. Nobody earns more than that. Nobody earns less than that.

The only thing to be negotiated is whether you're at the top, middle or bottom of that scale.

Sure, you might find out that someone is earning more or less than you, but it won't be by much, and if you knew roughly what you would be earning before you even applied to the role, you wouldn't be worried too much about what anyone else is getting.