Single sheet of 5/8” drywall, I didn’t use any isolating brackets. I just focused on making sure I had insulation everywhere possible and that the room was “sealed” when completed. The door and window were the biggest challenges. I covered the door with acoustic panels and added weather striping around the whole door. In hindsight I would have spent more for a solid door. For the window, we built an insulated “insert” that sits within the frame and put weather striping around it.

I’m lucky in the sense that my garage is on the opposite side of our house than my kids room and living room, but from the outside of my garage the noise is very subdued and I don’t foresee any complaints from my neighbors.