The space is not that large so you'll be limited on how much variety you can have. I'd reconcile that you will have either evergreen, such as a Yew, OR flowering, such as a Hydrangea. But not both. (Many Hyrdrangeas hang onto dried flower long into the winter so still add interest once they thicken up.) Trying to do one in front of the other is going to be a failure in some way. Good form will be your friend. Even a plain, flowerless evergreen can be stunning if its form and complexion are impeccable.

i am curious how much the 4 stage treatment cost .. would you mind telling us ... if the problem is solved ... and it should be solved .. and the tree ought to recover ... period ... you shouldnt be thinking that it will recur.. if it was a completed job ... so there is some logic in waiting and seeing.. what happens this year... and suggesting to the service that provided such.. that they most likely promised to solve the issue ... on the other hand... i can see the logic in being done with it.. since every time you see it.. your blood pressure probably spikes ... lol.. mine would ... i would give it.. in tree time.. at least this year.. to see the result of the money you paid .... and then go from there.. in other words.. i would be watching in tree time .. not instant gratification time .. anyway ... im at a loss how to suggest a tree for a spot in your garden.. without seeing the spot in your garden.. and its relation to the house.. etc .. how about some pix .. and we could confirm the ID with a pic of the plant and its leaves or flowers ... but i sure hope your service provider actually knew the plant ... ken btw: clay is not a tree choice issue.. its a planting issue which i easily dealt with .. EVERY ball and burlap plant you see in a nursery ... was grown in clay.. else there would not be a ball in the burlap ... you sure cant do that with soil that falls apart ... and the stuff that doesnt fall apart.. is clay ....

With a long property line I would suggest grouping different plantings in areas. Areas wanting complete blockage put a group of 4 or 6 evergreen. Areas with less then deciduous. Some variation with specimens interspersed. When space allows you can layer shorter in front of the taller hedge. You can use a tape measure for spacing and also pay a little more for larger plants (even pots at $29.99 instead of $19.99 isn't much more if you can't afford the B&B price). The Emerald Greens and your spacing looks like, even when mature, they will be just lone monuments along the prop line. Every box store in your area loads up on cheap Emeralds, but that doesn't mean it is the best plant for your use.

Based on the shade, I go with mt. Laurel and azaleas. There are plenty that will be about the right height. Mt. Laurel minuet, for example. Azalea Weston's lollipop. Dwarf Fothergillia. They will do well with part shade. If you have sun, you have more choices, but I'm not as sure of them, given that my yard has part shade, shade and deep shade. Try Bluestone perennials. They have plenty of shrub choices.