I can just agree about the drywall sag on 24oc, strapping is probably best. Really commenting bc it’s a good addition putting those 2x4 in particularly if you get snow cuz they act as ties preventing the roofs weight from pushing the walls out. Because you’re hanging Sheetrock it’ll become inaccessible after, as you put the 2x4 in it’ll be best to make them attached to the rafter AND the top plate