So, the Ruler Customizer changes I make in one part of the world carry over into all of my new games. What's the easiest way to revert everything back to default on all new games?
There are a lot of issues with starting a new game without doing a shutdown and restart of the CK2 client.
I would recommend doing this every time you wish to start a new game. A bit of a pain, but, it ensures a clean new game.