Lex: while photos are extremely helpful to us in visualizing the situation, the one you provided is not doing your garden justice - it's a bit too small and the panorama effect distorts the perspective. Is it possible for you repost with individual photos of the garden areas rather than a panoramic composite? And a quick plan sketch with some measurements would be equally helpful.

Beyond this, suggestions will be unfortunately vague :-) Depth of available planting areas will determine to a large extent what can be used successfully for screening as well as layering.......and if this is your intent, it is best to err on the side of generosity.

And some quick thoughts on plant selection. It's impossible to see from the photo provided where formalized, sheared hedging may be appropriate. Arborvitaes are ideal for taller formal hedges and pruning or shearing is optional, as many (like the Emerald Green) are by habit narrow and columnar. For shorter hedges, box or Japanese holly are popular and for good reason, but germander, rosemary, even lavender could work in the right situation. Formalized hedges require ongoing routine maintenance to keep them looking sharp, so keep that in mind when making your plant choices - don't select a shrub or tree that naturally wants to grow to 20+ feet when all you are looking for is an 8' hedge.......too much work involved :-)

Otherwise, an informal screening as a backdrop for lower plantings is relatively easy to achieve, provided the depth of the planting bed is suitable. A mix of evergreen shrubs/small trees and deciduous plants will accomplish this, with the weight placed on the evergreens. Your second group of listed plants could comprise the bulk of this, but I might consider replacing the viburnum choices with the evergreen V. tinus and adding Choisya ternata, camellia or smaller selections of Hinoki cypress.

I am personally very fond of fastigiate hornbeams for deciduous screening purposes and use them often in designs. Their very upright and dense branching structure makes them pretty effective for this purpose even out of leaf. Carpinus betulus 'Frans Fontaine' is my cultivar of choice.

And some of your listed plants are just not well advised for your area or for the purpose you have in mind. Butterfly bush is a listed Oregon invasive plant, redbuds tend to be rather short-lived in the NW, sumac suckers aggressively and over a wide distance and privet has a host of issues that make it a less than wonderful choice.

Hope this will be a start to get you thinking. And come back to us with more photos if you can.