I don't know if anyone have experienced these, but it seems AI is founding way more cities (7 or 8), before Code of Laws and Currency. I don't understand how they can keep up in the tech race and still pay the maintenance for their cities. This didn't happen in 3.13. I'm currently playing with Elisabeth (Philosophical and Financial, which seems a very good treat combination) and I can barely mantain 4 cities (without losing the tech race) before Code of Laws and Currency...

You're obviously not spamming enough cottages or working on your economy then. It's easy to maintain 7 or 8 cities in the same situation and still be competitive.

I have noticed this too. I find I need to spam 14+ cities on a huge map to keep up with the AI city building.

On my recent game the Babylonian had 16 or so cities. After 2 wars I took out 5 cities or so and their capital but they still had 13 or so cities. Longbowmen are a pain to attack so I needed trebs. I kind of think their capital was holding them up as their science was poor. I razed all 5 cities as they were surrounded by cultural borders and i was already struggling to keep science above 20% even with market places. Problem with razing is the Ai just rebuild new cities in the empty land. Losing their capital will be a huge blow!!

I think my science is being offset slightly by representation and specialists.

I think if you take out 1-2 civs early on a huge map it opens up land for other civs to expand and become much stronger.

So basically let your cities grow in size fast and use lots of cottages early on for science. Also build lots of workers early on. Even on a non financial civ this is possible.

i dont think 3.17 made them any better in monarch but theyre definitely quite expansive as you say.
but i found that by playing mehmed of the ottomas i could match their expansion and keep research high because of his beautiful trait and UB combination which allowed me to build huge healthy cities full of cottages.

spam cottages!!!