Air sealing at an attached garage is intended to reduce uncontrolled movement between the garage and occupied space. It is a building-science intervention, not a substitute for every fire, combustion, or code requirement.
Ventilating an attached garage can affect pollutant movement, pressure, noise, moisture, and the house's air-control strategy. An exhaust fan is not a universal fix and should be designed around the actual garage and adjoining spaces.
Garage insulation is an assembly decision, not just a matter of adding batts between studs. Walls, ceilings, doors, air sealing, moisture, adjoining rooms, and the garage-house boundary all affect the scope.