Is God universal and necessary, or particular and contingent?

I don't know. God is some sort of mix.

In part, God is universal and necessary. This is similar to how 2+3=5, even if there are no humans around to think that. There's no magical object of a "2" sitting around, that you can bump into like you can bump into a rock. But it's still a Thing. You could say that "2" describes and is manifested in the situation of two particles, or two rocks. And there is the transparent crystalline platonic realm, where 2 has eternal canonical logical connections to other things.

God is more messy, more contingent, more complicated, because God is humane (though not human [TODO link person]). So God is a mix of this simple, platonic logical structure, and also messy contingent stuff. Analogously, a government is a mix of abstract universal structure (Justice, rule-following, natural law, natural rights, separation of co-regulating powers) and particulars that can be chosen (which people get which powers, which areas get what representation, what priorities to have).