Would arborvitae work? Would you consider creating more sun so you have more choices? A 15-foot trellis wall doesn't sound pleasing to me. Have you checked out what tall shrubs or short trees can take some dry shade in your zone?

Don't you just hate that? My neighbor actually installed security cameras on his house directed right over our patio and it is legal for him to do so! I'm probably on some webcam every time I go out to water etc.,(how boring). Anyway, we planted serviceberry trees with arborvitae inbetween, (the arborvitae take too long to get big enough) and then we strategically placed wires (to block camera) and planted wild grape which fills in fast. The benefit is great bird habitat! Good luck, it's so hard to find privacy anymore :(