I think it's faster than anything in the CFC HOF above Settler (lowest) difficulty level. That one lets you pop settlers from ruins, so it's a whole different game in terms of acceleration, and there's some results in the 140s.
City-states (maritime and mercantile) are quite valuable in terms of time-to-launch, could be as much as 10 turns over having none of them. AIs are not so important, you gain a few turns by a worker steal or two and ideally a ceded city for peace, but beyond that they're just a little money for your resources, except on Deity where you can steal a lot of techs. I don't really know how much Petra gains; I did miss it one or twice in earlier games but there's way too many variables to isolate it and I have no reason to want to try.
City-states (maritime and mercantile) are quite valuable in terms of time-to-launch, could be as much as 10 turns over having none of them. AIs are not so important, you gain a few turns by a worker steal or two and ideally a ceded city for peace, but beyond that they're just a little money for your resources, except on Deity where you can steal a lot of techs. I don't really know how much Petra gains; I did miss it one or twice in earlier games but there's way too many variables to isolate it and I have no reason to want to try.