Director Steven Maler keeps the energy level high, the pace rapid, and the action clearly delineated. He astutely gives free rein to a pair of inventive performers who have been standouts in earlier CSC productions, and are so again in “Twelfth Night’’: Fred Sullivan Jr., as the ludicrously pompous Malvolio, and Remo Airaldi, as Feste, a Fool who wears a Harpo Marx-like top hat.