React is pretty performant when context isn't changing. We haven't done any benchmarking but I doubt there's any real world perf hit. For large applications the number of overrides tend to be under 20.
Overrides are opt-in so you can just expose any overridable value as a prop and run a isolated component test on it.
Overrides are opt-in so you can just expose any overridable value as a prop and run a isolated component test on it.