The original recipe calls for 1 cup each of chopped almonds and cashew halves, but I usually just throw in whatever nuts I have available - walnuts, pecans, almonds or cashews - or a combination of a few of them. Don't eat nuts? It's fine to leave them out, too.
It's also fine to throw the white chocolate chips in with the rest of the ingredients, but they WILL melt if you pour the syrup mixture directly on top. I prefer to have my chocolate chips stay intact, but I've eaten this Chex Mix with melted white chocolate throughout, and that's pretty amazing, too. It's all about preference!