To what extent are the underlying models fundamentally different,
compared to just being the same thing with the controls set to different positions?

e.g. it seems pretty clear to me that the Yamaha CP-80, and the old 18th century pianofortes and the harpsichord are fundamentally different underlying models, and no amount of control tweaking will make them sound like the "C2" grand piano? Is that correct?
But what about, say, the various "concert"/"chamber"/"mellow"/"bright" etc C2 grands?
Are they all just the same thing, only with handy different starting points for the sliders in the UI? (although each preset appears with its sliders set to the defaults, I'm thinking they've been tweaked before hand?)