The first changes to this game I would recommend after playing 40+ hours

[Chronicler]

You haven't looked at their National Idea set though

Traditions:
+0.10 Yearly inflation reduction
+0.5 Yearly republican tradition

Founding Fathers
-33% Advisor costs

Continental Trade
+25% Provincial trade power modifier

Religious Outposts
+3% Missionary strength

Free Thinkers
-10% Idea cost

Colonial Militia
-10% Regiment cost

New Frontiers
Terra Incognita adjacent to colonies is revealed.
+20 Global settler increase

Liberty Heroes
+1 Leader(s) without upkeep

Ambitions:
+10% Morale of armies

Actually I have, and +20 is still not enough for -25 tropical. I also assume they are not advanced enough to realize Colonial Expansion is the best early policy for them if they can even pick policies, Expansion has +10 settler growth, I don't know if they pick Exploration. So unless it's like +30 it doesn't really matter :/.