Most meaningful React performance gains happen before memoization. They come from deciding what must be interactive, where data is fetched and how much JavaScript crosses the network.
Server-render stable content and isolate small interactive islands. This lowers hydration cost while keeping the experience responsive where it matters.
Measure real user outcomes, not only lab scores. A smaller bundle is useful when it improves interaction latency, loading stability or the speed at which a user can complete a task.