And finally I'm confused about these old event chains one guy mentioned. What's true now? Do they trigger or are they at least supposed to trigger (maybe depending on which policy you take) or are they turned off with Cossacks?
The event "Natives Encountering our Colonies" cannot trigger if you have the DLC. The Native Policy system takes over what this event did.
If you have the Repression policy, you can get these events:
Native Raids - Requires at least 5 aggressiveness, 300 natives, no units in province, colony of at least 200. Allows you to increase aggressiveness and ferocity, but reduce number of natives and slightly lower colony size. Or slightly increase aggressiveness and ferocity at the cost of a larger number of settlers.
Native Exploitation - Requires at least 500 natives, colony less than 200 settlers. Lower the amount of natives in the province, and give you a country modifier that lowers settler chance and growth, or pay 40 ducats and get a modifier that increases settler chance and growth.
Colonial Expansion - Requires ruler with MIL 2, and a neighboring province owned by you. Increase the number of settlers in the colony by 200, pay 30 ducats, and get a country modifier that slightly increases settler chance and growth. Or increase the number of settlers in the colony by 50 and get a modifier that lowers colony growth.
If you have the Trading policy, you can get these events:
Lucrative Trade - Requires at least 50% trade efficiency, and a neighboring colony owned by you. Option to gain 50 ducats, or a modifier on the province that gives trade power for some time and 10 ducats, or gain 20 diplo points.
Spread of Disease - Requires less than 200 settlers, and at least 500 natives. Same effect as Native Exploitation above
If you have the Coexistence policy, you can get these events:
Religious Influences (protestants) - If you're Protestant and the province isn't, and less than 4 aggressiveness. Option to increase the aggressiveness and ferocity of the province as well as change the religion of a colony to protestant. Or lower the aggressiveness and ferocity of the province. Useless event if you ask me...
Religious Influences (catholics) - If you're Catholic and the province isn't, and less than 4 aggressiveness. Option to increase the aggressiveness and ferocity of the province as well as change the religion of a colony to catholic. Or lower the aggressiveness and ferocity of the province. Useless event if you ask me...
Spread of Disease - Same as Spread of Disease above.
You can get these events regardless of the policy you pick:
Native Assimilation in [province name] - Requires a unit stationed in the province, and at least 300 natives. Increases the number of settlers by 100.
Accommodation with Natives in [province name] - Requires a unit stationed in the province OR the Coexsistence policy. Also requires at least 300 natives, 1 ferocity, and 1 aggressiveness. Lowers the ferocity of the natives in the province (useless if you're running Coexistence).