Colonial AI seems remarkably stagnant no matter what. I have a CN that owns ALL of the Eastern US (except 2 or 3 FL) and they only have like 7 soldiers and won't even managed their own rebels. Not a single one of my Colonial Nations (I have 5) has ever colonized a province on their own. I don't know if this is because I have artificially grown them by adding Spanish/indian/portugese territory and they spend time culture/religion converting over colonizing or what. The only one I even changed tariffs on is the Eastern US one. They are remarkably lazy about attacking or using their armies or anything. Every time I get in a war with Spain 2 or 3 years go by and then about 20k guys show up in SA in Guyana from Castilles MASSIVE SA colonies (almost all of Brazil and Plata) and I murder them and that's all for them. They at least are colonizing though.
This I don't see though,
Most of my CN's colonize on their own, especially in Brazil, Canada, Eastern US and Columbia.
I have never seen the Caribbean AI colonize, and I've have had CN's that wouldn't colonize. When that happens I keep sending them Diplo leaders over and over until the start. Once my Guyana CN never once used a colonist.
I've also seen solid CN wars and army management. I've often had my Portuguese Brazil attack Castillan La Plata and have a good fight. My recent French game, I have 3 CN's Caribbean, Canada and Eastern US.
Caribbean isn't doing anything but sending me money and sitting around, but Canada and Eastern US have 8 and 10 regiment armies so far with 5 and 6 provinces respectively and they are keeping their own revolts down, converting different religions, and colonizing.