We would like to insulate and drywall the garage ceiling to work on projects in the cold winter and hot summer. (We'll probably install a mini-split or something similar, too.) This question is specifically about the ceiling (but see this question about the walls).
This reference says we need to target R38-R60 in Zone 4 for an attic space...but the garage is not an attic. In addition, the rafters (pictured below) are 2x6's on 24" centers so R23 is about the most we could get in with batts.
Question: What is the best practice to insulate (and drywall) the ceiling in situations like this?
Picture of the garage rafters: