Nice post. From my understanding it falls under Works, but has grace in it. But I'm not sure so I'm reading Robertson's Christ of the Covenants and the Witsius' Economy of the Covenants. Which is available online.
But I did notice you didn't use the typical word found in older Reformed literature when referring to how the covenants are disposed.
It ought to be remembered that the imperatives of the Law are preceded by the indicatives of grace (see prologue in Ex.20). 'Both / and' is a nonsense. Luther warns us against turning Christ into another Moses.