Not a bad idea, but not required from what i have seen in my state (idaho has lower standards generally, so im not surprised.)

I have never seen double layers of drywall.

At least 1/2in drywall with filled cracks all mudded and gaps filled. Foam or firecaulk applied where any plumbing or wires pass through the drywall.

Doors must be solid (20min fire rated)

All havc duct must be metal.

Edit: passage door from garage to the reast of the house should be 20 fire rated, and typically you want self closing hinges. (The hinges code has come and gone and come back again last i saw. It keeps out car fumes.)