I agree its situational, but on deity which I've just recently started playing, spamming of AI cities is crazy fast compared to other levels. I'm finding that, on most maps, if I restrict myself to 1 city, by the time it comes to build the NC I will have aggressive and close neighbours, even if I didn't before... So it seems to be important to get a second, possibly even a third city out there asap to claim the good territory. My general approach is Liberty, take the Collective Rule policy to get a settler out quickly, hard-build the Library in the capital, rush-buy it in the second city and then hard-build NC asap after Philosophy. Take out a GPT loan from a neighbour to assist in buying an early worker to generate the cash for rushing an early worker and library in city 2 (assuming you can't "acquire" one from a nearby city-state). Chopping forests while building the NC really speeds up production, especially if the capital is not a production powerhouse and for example you have calendar instead of mining luxs. I'll experiment further with a third city, although this obviously delays the NC unless you are cash-rich.