Insulating attached garage – drywall over sheathing or vice-versa? – GreenBuildingAdvisor

I’m insulating (rockwool) the wall between our mid-century home and the attached garage.  Garage was built with the home in 1964.  I intend to add strapping to the 2 x 4 wall to make the wall effectively a 2 x 6 wall.

I’d like to finish the wall with exterior-grade siding (SmartSide or similar), which brings me to my question:

Can I put this over my type-X drywall (not present, I will install this) without affecting the safety rating of the drywall?

Thank you.