Box-Behnken method is one of the design space exploration technique. If this technique is used, the variables involved in your design of experiment will take different low, medium, and high values governed by the Box-Behnken method. If  the RSM's R^2 value is satisfactory for your application, then one may proceed further with optimization or another DOE technique , such as genetic algorithm or NSGA-II may be chosen for exploring the design space exploration. I hope this helps.