The AI is just a gosh darn cheater in this and always has been. You can plan around it (what's that Mr AI? You get a nice early settler that you'll move unescorted to a prime location right at the start; be rude not to take that from you) but it has always been the biggest issue with the franchise. I've got them all and it has never been particularly good. Forward settling as been curbed quite a bit by the loyalty mechanic so that's nice but my biggest ever issue is still present and still really gets on my teets and that is that if you have a unit close to another civs borders they will tell you to move it or make a DOW but you have no option to do the same when they blatantly move their units around your borders getting them into position for a sneak attack.
I've played nearly all the new civs up to the Renaissance ear (not tried Shaka yet) and thoughts are:
Cree - Very strong early game. If you get lucky with resource placement their UI is amazingly powerful. Absolutely must have as many trade routes as possible to grab that land.
Georgia - Have to go full on faith to get the most out of them. It's actually useful now though with the 2nd tier government plaza building which allows you to buy military units. Combined with Theocracy and the Monument GA option you can just faith buy your way to complete dominance. UU is a bit of a duffer.
Dutch - Haven't accessed their UU or the polder yet so not much to say unfortunately.
Korea - Set up loads of Suwons early on and you'll pretty much be guaranteed to get every Great Scientist available, such is their science power unless you meet..
Scotland - Potentially so OP it's not funny. Get plenty of amenities to get your populace ecstatic, build as many campus' and IZ's as possibly and sit back and laugh as you take any GP worth taking, leaving only the duffers as crumbs of comfort for anyone else; especially fun if you have Pedro in your game, just to make him
really butthurt
Mongolia - I find you get the most fun out of him if you tinker with the start settings so all your rival civs are ones with horse based UUs. That way you can steal all their special units and turn them against their old masters. Mwhahahahaha.
Mapuche - Can get a shed load of culture early on if you get lucky with breathtaking level tiles due to their UI. Their loyalty reducing mechanic and extra power are both very situational. I've not yet had a city settle so close to me that I had an opportunity to kill their units to flip it, and the AI is a bit pants at getting Golden Ages so again, not had a chance to test the power of the extra attack power.
Governors seem a bit meh, except for Magnus who can pretty much gain you any wonder you want if you have trees around to chop. Not particularly fun, nor environmentally friendly but hey, we're in a game that promotes whaling and catching endangered turtles for fun so what the Hell