Zone 5 Northern Illinois.

Hello! Thought I would post because I am stumped and everyone here is so graciously helpful. Even though our neighbors behind us are wonderful, the houses are so close together we wanted to add a privacy screen along the back fenceline. We do not need an impenetrable wall...I just want to feel less exposed. I also didn't want the entire run to be arborvitae, so a young landscaper advised that we just put the Emerald Green Arborvitae (currently 6' - 7', maturity 12' - 15') for the width of the neighbor's house and then we could "fill in the sides with whatever you like". I just planted an interesting tree to the right of the shed....Goldspire Ginkgo, very columnar variety that is yellow in the fall and should mature to 14' - 16 tall and 5' - 6' wide. We will see how it works.

I am however, stumped with the right back corner. Currently there is a white hydrangea that just doesn't feel right after we put the new fence in last Fall. Part of me wants to put a larger, darker green Juniper in the furthest corner that gets up to 20', then in between that and the arborvitae put a columnar dwarf blue spruce just for some different texture and color, but then I fear its too much "tall". My husband would like to get a lilac tree in that back corner (8' to 10' tall), and then put a skinny blue-colored juniper (10' - 12') in between the lilac and the arborvitae, but then I fear a "shorter" bush at the end of a tall line is going to look awkward. I just don't know...I don't know the rules. I want it to feel organically balanced but not a mirror image. Any ideas or recommendations for this area for Zone 5 northern illinois? I've outlined the area in a white box. The area is 16' wide. Whatever we put in here needs to stay under 25' because of the power lines (ideally). Thank you so much!