I don’t think it does. Discretion is fundamentally case by case. Drawing categorical lines is legislative.

It’s akin to the distinction between law and equity courts at common law.

Stepping back, both doctrines (non delegation, unitary executive) are fundamentally about the courts overstepping. If both houses of Congress pass a law creating an agency with a director that can only be fired for cause and the president signs it, the Supreme Court should stay out of it.

Enacting legislation is very difficult, the presumption of constitutionality should be taken more seriously.