So libertarianism seems to be about maximization of negative freedom, minarchism, and a faith in free market capitalism. Is this alien to classical liberalism? In another thread a commenter claimed classical liberals weren't as strong supporters of the free market. I'd read about South America, where liberals supported the state taking over duties of the church (marriage, cemeteries, birth registry), which I can only assume libertarians would think statist and unnecessary.
Is classical liberalism a single ideology, or a collection dependent on location? How similar are libertarianism, neoliberalism (the Friedmanite kind), and social liberalism to classical liberalism?
Isaiah Berlin's Two Concepts of Liberty is quite good at unpacking the central difference between social and classical liberalism i.e. positive v negative freedom. This is basically the root debate of liberalism, and while libertarians, and neoliberals differ from classical liberals, they are all united in that they fundamentally believe in negative liberty. The state is thus fairly non interventionist. Social Liberals, meanwhile, think freedom is about enhancing oneself, and so the state should intervene to allow this (see the British welfare state, Beveridge argued a starving man is not free).
The main issue you have here is that no two people will ever have the same views; classical liberalism does not exist in one place nor does neo liberalism. As such its hard to strike a clear line between them because it subjective where you draw it, the words themselves show this in that its a divide between new and old.