I think some of the difference may come from playing smaller map templates. One thing that took me a while to figure out is that "Standard" map size only sets the number of civs/city-states/etc, not the physical size of the map. A "Standard" Lakes is actually much smaller than a "Standard" Highlands, for example.
Most of the people doing fast science victory over at Civfanatics stick to the most cramped map templates (Lakes and Great Plains). This means you meet both CS and AI faster. I am generally very aggressive about taking gold from all AIs as fast as possible. Caravan plunders are 100g, tile pillaging is marginal but adds up if you do it a lot, free Workers are good... then you take gold from them in peace deals. You can sell both resources and embassies for lump-sum gold in peace deals, and can even use this to take loans without DoF. Eventually they will start paying you for peace (they seem more willing to do this if they have more than one city, for some reason). I DOW AIs for peace deal gold even if my units aren't taking anything from them.
You can do this on larger maps, too, but it helps to meet AIs very fast. On the other hand, big maps mean more ruins, more AIs, and more CS gold, even if it takes longer to meet all of them. Similarly, higher difficulties mean more AI gold, but have other drawbacks. It's really hard to know which settings are optimal. I suspect Huge size with one of the cramped templates is probably very strong.
Most of the people doing fast science victory over at Civfanatics stick to the most cramped map templates (Lakes and Great Plains). This means you meet both CS and AI faster. I am generally very aggressive about taking gold from all AIs as fast as possible. Caravan plunders are 100g, tile pillaging is marginal but adds up if you do it a lot, free Workers are good... then you take gold from them in peace deals. You can sell both resources and embassies for lump-sum gold in peace deals, and can even use this to take loans without DoF. Eventually they will start paying you for peace (they seem more willing to do this if they have more than one city, for some reason). I DOW AIs for peace deal gold even if my units aren't taking anything from them.
You can do this on larger maps, too, but it helps to meet AIs very fast. On the other hand, big maps mean more ruins, more AIs, and more CS gold, even if it takes longer to meet all of them. Similarly, higher difficulties mean more AI gold, but have other drawbacks. It's really hard to know which settings are optimal. I suspect Huge size with one of the cramped templates is probably very strong.