First of all, I strenuously object to labeling political ideology on only one axis.
Second, I'm not sure what "populist" even means in this context -- authoritarian demagoguery, a-la Trump (or Hitler)?
Third, as a fiscal conservative / social liberal (or left-libertarian), I picked "libertarian" since it seemed closest out of the choices provided.
Interestingly, this "libertarian" is voting for Bernie Sanders -- despite the stuff about free college or whatever -- because he's got much more respect for civil rights than any other candidate (even respect for the Second Amendment, although he appears to be attempting to pander to the anti-gun nuts at the moment) and because unlike any other candidate, he recognizes the danger to society and democracy posed by the corporate elite.
Now, you might think that last clause sounds like the opposite of libertarian, but it isn't. The "danger posed by the corporate elite" is enabled and caused by government regulation. It's not regulation that restricts what corporations can do; it's regulation that gives corporations unfair advantages above and beyond what natural persons have. For example, the fact that officers are not held personally liable for the acts of the company causes them to act like sociopaths and the recent Supreme Court ruling allowing contracts to force arbitration and disallow class-action is unconsionable. Because of the limited-liability nature of corporations, it is entirely necessary and proper that they be subject to reasonable regulation (anti-trust, Glass-Steagall, etc.). And that is not any sort of limitation on freedom whatsoever -- if you don't like being subject to corporate regulation, you're always free to be a sole proprietorship instead!