I opted out of a class action settlement once (the Google/Apple/etc wage fixing lawsuit). The opt-out did absolutely nothing except that I didn't get a check but I did retain my right to sue. The tart letter I wrote to the judge about the quality of "my" attorney, though, that got a reaction. Not from the judge, but from those attorneys. They went from "won't return your email" to "very concerned to make sure I was satisfied". Only time I've ever had a lawyer dance for me.
The opt-out isn't really supposed to "do anything," because it doesn't necessarily mean you disagree with the settlement, just that you would rather litigate on your own in your specific case.
