Yes. Memoization is not free, and using these hooks for cheap computations, without a memoized child, or with wrong dependencies adds overhead without benefit. The default should be no memoization, added only where measured.

No. useCallback only helps if the child receiving the function is wrapped in React.memo. If the child is not memoized, it re-renders anyway, so the stable reference provides no benefit and the overhead is wasted.

Missing dependencies cause stale values; too many cause recomputation on every render. Wrong dependency arrays undo the memoization, so you have overhead without the benefit you expected.