We are trying to find the best way to make a games review site. We want to have a custom Post type that has all the information about the game. We want to have a news category and review category (potentially a review custom post type).
Two questions, is there a way for two related posts (say game and review) so the meta fields are filled in from each other if empty.
The extension MB Relationships only support create connections between Game posts and Review posts. It does not help to auto-fill field values from each other. You can create custom code to update/set value for a field with the helper function rwmb_set_meta(). Please get more details on the documentation https://docs.metabox.io/rwmb-set-meta/