starting with walls vs ceiling
I'd put the rip at the top for the convenience of finishing. Or maybe I should say to save all the bending over to finish at the bottom (the old back will appreciate it). And definitely break the butt joints over/under the windows or doors. As you can see in the illustration above, you'll have a 2' or so joint to finish as opposed to a 4' joint. Less work, less mud......
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