Posture for a pitcher

[Shake Zula]

I've heard of a lot of theories of the posture for pitchers. Paul Nyman of SETPRO stated that arching-unarching of the upper body (bow-flex-bow sequence) is effective while Sandy Koufax (who was a mechanics savvy) stated about 'low and wide' and I heard a lot of coaches say stay tall. All these opinions confuse me, would anybody help me out on this?

[XV84]

By "posture" do you mean "spine angle"? All efficient pitchers bow-flex-bow. Koufax did. Are you saying he doesn't?