The seahawks plays mostly cover 3 and some cover 1. Usually sherman does a deep drop so you usually can complete a lot of passes infront of their CB's. For example if you are running slants and crossing routes, rarely is sherman going to be following them across the field.
They play 1 deep safety and keep the box loaded mostly to stop the run. With the way they just drop their CB's back right away it makes it tough to throw the ball deep on them especially if their pass rush is getting there. in third and short you may get them to get in cover 1 with 1 deep safety, I believe that is where where you have to take your shot if you think you need to.
Against the packers they probably will be a bit more careful and hope for the front 4 to stop the run, if that's the plan you need to be able to run the ball.