I don't really know much about landscaping, Jazzy. Yews tend to grow straight up and should be okay, I'd think, in zone 4.

Years ago, Dad took some lilacs that were kind of out-of-hand on my property. He planted them in the corners of his backyard. Then the neighbor on the other side of the fence (not a nosey kind), planted lilacs all along the fence line between these 2 corners. So there's a 90' row of lilacs.

Now there are suckers on both side of the fence and this area would turn into a jungle without constant pruning. The lilacs are at least 12 feet tall and, along with the fence, they've certainly shaded that part of the yard and restricted the movement of air. Mildew has become a serious problem with the other plants.

Don't mean to be too negative - I like lilacs. And, they may be able to do what you are hoping for. Yews and any evergreens are likely to be more slow in growing.

You may want to ask this question on the forum linked below.

Steve

Here is a link that might be useful: Landscape Design