Let me share my experience (playing as France on Emperor difficulty, pangea with some inland seas).
Let me start with positives:
a. AI is more aggressive in the beginning and much better attack cities. In Classical era I again left my capital poorly defended and China AI made really good effort almost taking it. they sent good military force (4 warriors + slinger) and they really tried first to siege it and then take down defence. However, for some reason at the moment when they could've taken my capital (just one last attack), China offered peace paying 1gpt! Mb AI tried to save its damaged warriors, but still a bit stupid move.
Although not ideal, siege process really improved comparing to what it was before. I'll check how it will work with AI+ or AI cleanup, mb these mods will work differently with the new patch.
b. AI settles in a good locations, prefers rivers/seasides and avoids empty desert. Also, AI usually settles new cities at a distance of 3-6 tiles from existing ones - sometimes it's 3 tiles when there is a lack of space/close enemy border (which is imho smart thing to do) but in general settling process is fine. Also there is no insane settlers building - AI spreads steadily. Overall, I think this part is fine (although need to test island maps).
c. Looks like AI understands how to use city-state army. In my war against China city-state army marched to my city and seiged it - it was soo nice surprise (screen attached). i don't know whether CS did it or China AI bought its army but it is really great. This helps to eliminate over-spamming of CS units.
d. AI builds good number of districts and really competes for GPs - I managed to get only one great scientists and when I look on Great writer points some unmet civilization producing 16 GW points per turn(!).
e. AI builds wonders actively - I couldn't get any wonders (and tbh construction costs are ridiculous for many of them) in my game. AI tries to build them straight after researching the required tech.
Now about negatives:
a. AI peace offers are still weird. Mentioned above peace was strange but didn't impact on the game. However, during my second war with China I managed to take one of their cities and killed many units (however AI still had sizeable force).
They offered at first 37 gpt (before city was taken) and then after it they offered 4 luxuries and insane 102 gpt! This was at medieval age and I didn't see many ai caravans so I suspect AI somehow cheats when makes these offers. It really breaks the game...
b. Warmongering issue: I took one city at Medieval age in a defensive war and got denounced but literally everyone. I think this leads to smaller number of wars and as a result AI doesn't lose their units, leading them to concentrate production on workers/districts/buildings.
C. AI snowballing: I don't know how much is the AI production/science bonus on Emperor difficulty, but I played with less science per pop (city spec mod, 0.50spp instead of 0.7) and smaller tech boosts. And still, brazilian AT crews in 1470ad! I guess if Sumeria would be in the game, I would see modern armor at that time. AI bonuses need to be reduced and some penalties/bossts needs to be added for being massively ahead or behind in science.
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