Ideally there would be three ways to colonize a province:
1. A trading post, which will cost you a merchant. This type of colony would net you trade income and would only slowly grow into a (colonial) province
2. A mission station, which will cost you a missionary. This type of colony would result in the conversion of the province and would grow faster than trading posts but slower than plantations
3. A plantation, which will cost you a colonist. This type of colony would result in the culture become your own and it would grow the fastest of all
Even more ideally, multiple countries would be able to colonize the same province at the same time. The one that gets to the magic number first, gets to own the province and half of the others' settlers (many Dutch stayed in New Amsterdam after it was sold to the British). There'd be ways to reduce the others' settlements (attack it or buy it up, etc.)
The province would then become a colonial province and unless it's on the same continent will never become a regular province (Russia is an example of same continent). Colonial provinces would behave differently from normal provinces (in EU3 there was no difference between a colonized Maine and London).
+1 And I strongly agree with 3 possible ways of colonization.