Remix's "Fog of War" feature dynamically loads route information based on user interactions. This optimizes React Router SSR applications by decoupling rendering from fetching, resulting in a "fetch then render" approach that eliminates network waterfalls. It uses a Route Manifest to prefetch route data and components so that navigation is smooth.

While using useEffect for data fetching is common, it can lead to several issues, including race conditions, out-of-order responses, and inconsistent UI states. Remix's loader function, which provides built-in request cancellation, race condition prevention, and a smooth user experience, handles data fetching seamlessly. It also allows for custom loading states and provides flexibility and control over the user interface. Remix also has pre-rendering capabilities that deliver pre-rendered HTML with data included.