Massive production boots. Awesome farms, Every bonus useful. Economic bonuses kick in from the very beginning. Devastating UU.
Their start bias will guarantee plenty of mountains and hills, which is arguably the best start (mountains provide science, hills provide production and food for the incans, and mountains protect you).
I think it's already been covered that the mountains appear to be stuck at 2 prod. Which is sad; inca have 3 food boosting abilities, i think for the sake of yield balance they should have swapped one to production. (IMO the mountain adjacent to farms one.)
Let's also not forget that Machu Pichu was made for the inca, and if they get it then they get godlike districts on all those flat tiles next to mountains.
The best way to leverage the lnca is to spam cities in the mountains as tight as possible (and elsewhere with rivers) to maximize the number of aqueducts, and thus the number of times you get +2 production to terrace farms. (Technically you could roll a +4 if you have city-AQ-terrace-AQ-city.) The mountain/terrace interactions don't care what city has what tiles. Even if you only 2 or 3 per city, AQ+terrace farm is going to be a rampage.
The Warak is certainly going to be fun, but they still suffer form the vulnerability all ranged units have - the horse units can bulldoze through them. Warak are medieval, they dont come earlier. That same tech tier has knights and coursers, both of which can easily plow through your puny 20 defensive strength. Once they get Ambush, yes, they will be great- and I'm super excited to play them- but you can have 100 attacks a turn- doesn't matter if a coursers can basically one shot them.
In multiplayer we will have to see how tactically handy the qapac tunnels are. I can imagine being able to teleport down snaky mountain ranges will be pretty killer.
Maori - Uncertain. Balance completely depends on whether the devs will give you an "obvious" location to settle
I can see some variability around getting completely shafted in a tundra locked ocean or something. But I think they have 3 abilities that all tie so well together:
-More food from fishing boats/more production from woods/jungle
-The Marae is OP AF
-Toa are slated to be blistering ridiculous
You get free primary (food/prod) for either doing what you were going to do (fishing boat) or do nothing (woods/jungle.) You don't have to use more builder charges, you just get it. That's hammers saved for districts/Toa/whaetver.
+2 culture and faith on woods, reefs, etc, is absolutely bonkers. +5 yield on woods? aka 8 yield tiles at drama & poetry?! And you can still chop woods out if you want, there's no downside here.
The toa is also, imo, too good. a varu on the melee line (not vulnerable to pikes, and get oligarchy boosts) that can build a better fort than a legion can. I have strong doubts about the dev's ability to make this cost appropriate amounts. Legions are 110 and varu are 120 iirc. So you can have, once you get the 1st GP building up, a 48 strength toa with debuff aura that can build forts. That's fighting muskets at a -2 disadvantage for half the cost. We don't even know if toa need iron.
It's less about the first 10 turns settling and more about the next 300 turns of crazy bonuses.