The blog goes into detail of changes being made to policies, ideas and new concepts for modifiers, like splitting missionary strength. The video diary is a broader overview.
Project Lead Thomas Johansson discusses the new features the studio has with Wealth of Nations, which focuses more on the trade and economics of the grand strategy.
Policies are there to let us influence our nation through the decisions we make along the way, which have permanent effects and can be countered by other decisions down the line. Paradox wanted to combine these two elements into one with Policies, but they had a few more ideas to add.
"So, while we started with an idea about saving decisions we now have another layer of optimizing your nation, more flavour and a way to use that monarch power to boost a certain need you have at the moment," Paradox.
"...each policy is connected to two idea groups. To enact that policy you must adopt all ideas in those two groups. Each policy is also connected to one of the three monarch powers and as long as the policy is enacted it will cost you 1 monarch power each month. We have tried to balance to policies so that they cross over the monarch point categories a bit better to make it more interesting."
Modifiers have also been tweaked, such as Missionary Strength working differently against heretics and normal conversions. This means Counter Reformation is "no longer a brilliant tool to convert the infidels," but works great on heretics.
There are a number of balance changes to Ideas as well. Check out.