My insulated garage doors face southwest. The insulation makes a huge difference on surface temps and having them insulated is the biggest bang for the buck. I also have a mini-split HVAC unit installed but no ceiling insulation. I suggest you take a contactless thermometer and on a hot afternoon, test the insulated ceiling temps in each room of your house then determine the average. Then test 4 areas of the un-insulated ceiling over your garage and compare. In my case I had only 2° increase in temp of the garage ceiling. My HVAC installer did not recommend insulation over the garage but said insulating southwest facing doors was mandatory. A cheap contactless thermometer will tell you the story - no need to guess.
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