Running horizontal strapping is cheaper and faster than building stick frame walls....Why you would use just 3 spaced a 4' is beyond me. I would go every 16" or 24" OC personally. Then like others say glue+drywall. What a happy accident that you got 2" more closed cell for free.
Drywall anchors **** period and the screw in/ toggle bolt make a giant hole when they fail.
My original suggestion: You can put 2x6 boards crossways between the beams. One at floor level, and one at the 4' level and another at the 8' level. You may have to remove a little foam here and there, but basically just span the ten feet. I'd use 3" deck screws to fasten the 2x6s. Then just glue and screw the drywall in place. Buy 12 ft sheets of drywall and place them horizontally.
Not sure how you interpreted that as suggesting he build stud walls ?
Not suggesting that the 2x6s be vertical like studs. Studs support walls which support roofs. No need for that here as there is already sufficient support. My suggestion was to place horizontal boards between the existing uprights as they only need enough strength to hold the drywall in place. The thing I would be concerned about with plywood is that its more difficult to paint in a consistant manner. There is a tendency for spots and areas to "show" through the paint later unless you use some really expensive sanded plywood. Plywood will definitely be more a lot expensive, and as it swells and compresses with humidity and temperature. Gaps may appear at the joints.
Drywall will pretty much not change size, not have knots and swirls that appear later thru the paint, and cost a lot less to purchase.In a "garage that is used by people with mechanical hobbies, the cheaper grades of plywood can be used. The OP is basically using his "shop" as an extension of his living space and may prefer a more finished look. That choice is up to him and his pocket book.
As for the drywall anchors, they couldn't be any simplier to install and they are pretty easy to remove if necessary. Don't know what your definition of a "large hole" is, but removing one and filling in the hole is about as easy as any home repair can be. Two minutes to fill the hole, come back later when its dry, and another two minutes to sand it smooth. The ones I like don't have toggle bolts. See the attached picture.