Let's see, first game I played as the Mapuche vs. Gengis Khan. We spawned with two city-state between us. He was aggressively and successfully going to war with surrounding city-states. He took Hong Kong early on, then aimed for the two between us. I decided to defend and took one of his cities. I decided to let the city rebel and test out loyalty system and see how free cities are. Only problem is Gengis Khan kept threatening me because "You occupy one of his cities." Perhaps a bug?
I formed an alliance with Tamar and Tomyris early on. It takes a loooong time to level up an alliance, even with supporting policy cards for +25%. I think it could be easier to level up. Also, did they do away with defensive pacts? I assume so. Even with a cultural and scientific alliance, whenever I went to war with Gengis Khan, Tamar and Tomyris declared war on him as well. It's nice to see alliances be..alliances. That change must have slipped by me leading up to release.
Also, I went for a culture victory and civs were aggressively trying to trade for my great works. Nice to see, but annoying after awhile.