On possessions where you take the ball out of bounds , I think Harden is the primary ballhandler. Both handle the ball at different points of a possession …. on those that result from a rebound / steal. Initially you let Westbrook attack the rim and look for corner shooters and if nothing materializes kick it out to Harden who's the trailer and let him go to work either in the pick and roll or ISO sets. Basically you run a version of the 7 seconds or less offense with WB and if that doesn't work , pull it out and let the best offensive player on the planet do his thing. This limits the amount of 3's WB is taking while maximizing his ability in attacking the rim.