So I played my Spanish campaign until around 1650 or so, but am taking a break. I finished in first place with France not too far behind. I had the 2nd largest navy, the 4th largest army, and the strongest economy. I'm surprised that I had the strongest trade since I really didn't pay much attention to the whole trade steering sub-game. For colonies I controlled nearly all of South America and around half of Central, as well as Cuba and all but one of the islands in the West Indies. I also had a sizable chunk of Western Africa, nearly all of Australia and all of New Zealand. Plus a handful of assorted "resupplying bases" around the globe.
In Europe I had nearly the entire Iberian Peninsula, minus like 4 provinces that I left for Portugal. I also had all of Southern Italy (Sicily/Naples) and much of Central Italy and a couple of French provinces. I didn't go to the end, but I feel that I basically won. I may come back to this campaign, but for now....
I decided to start a game as France. So far I've managed to knock England off the mainland. Brittany attacked Provence and took them out. I had cores on their regions so I did a (in my view) daring attack against Brittany. Daring, because Austria was their ally. I easily fully captured all of Brittany's territories and had a sizable force to hold off some attempts by Austria to thwart me. I let the war drag on for long enough to fully annex Brittany.
Now I am working on integrating a couple of my vassals, since I have too many relationships. Burgundy created a war coalition against me, so I guess I need to go up against them. They are big, and that idea of that is scary. But seize the day, and all that. Starting as a very different campaign than I had with Castille/Spain, that's for sure. Good times.