A useful distinction
“Easy” and “hard” may hide different changes to timing, hints or allowed mistakes. Players can make a better choice when the relevant difference is explained. An option that changes appearance alone should not imply a different challenge.
Put it into practice
Write a short description of each option’s actual effects. Test whether changing it during a session preserves or resets the board, and tell the player. Keep difficulty choices separate from accessibility controls whose purpose is to make the same rules usable through different presentations or inputs.