IMO, the plant you are looking for is Lavender Starflower (Grewia occidentalis; sometimes sold as G. caffra). Zone 9a 9b 10a 10b. Sunset zones 8, 9, 12-24, H1, H2. You will want to espalier it against the fence, but they are one of the easiest plants to espalier--the branch form is naturally flat! My current plantings are in a narrow 13"-15" planting strip along the house, but I have used them in narrower beds. They may go into a bit of shock trimming the roots of a 1 gal plant to 4" wide for your footing reduction, but these are tough customers and I would not bet against them being able to overcome the rough start with a bit of extra care. Mine are currently about 8' tall and don't have any support other than resting against the side of our house, but a single horizontally strung wire would do the trick, if needed. They are generally listed as 6-10' height, but my SoCal experience is that espaliers easily reach 11'-15', if allowed. For all that, they are surprisingly quick and easy to keep pruned to form. They take heavy pruning like a champ, even hedging, and bounce right back. The foliage is a nice dark green, and the 1" lavender flowers that show up mainly in spring and fall are attractive and hummingbirds like them. Not messy plants--mine have never produced much litter. The plants grow quickly from 1 gal. size; they take a little while to get going, but then make up for lost time. They are heat tolerant, wind tolerant and, once they are established, drought resistant. Mine have never been bothered by pests or diseases.

Emerald Arb has a bit of a reputation of being more prone to winter burn then others, though I haven't had any problems to speak of. It is very tightly columnar, so doesn't knit together as well as others. I think Techny probably has the best overall look of all the arbs, dense but soft, and grows quickly, but will get fairly broad, 8 feet or so. Holmstrup is nice but grows slowly. I also really like the upright green junipers, like Spartan or Hetz Columnar. They have good berries and and dynamic texture if left unsheared. Also investigate the columnar forms of Scotch and White Pines or even plain old Black Hill's Spruce as part of the mix. Ted

What I've seen called "mixed hedges" in print were sheared hedges with active mixtures of leaf colors producing a calico effect. And hedges usually are linear. And very closely planted from the start. What you have is more like mixed border planting, with a grouping of this and a grouping of that. In an informal, flowing shape bed these would be drifts. This is why the trees being in a straight line is bothersome, it doesn't jibe with them having been placed in sets of several of each kind. And there is a considerable height differential between the Nootka cypress and the others. A good method is to choose shrubs that you expect to grow about 1 1/2 times as tall as the bed or other defined space they occupy is wide. Much beyond that and plantings can appear too tall. Your Nootka cypresses for instance, in this particular case. In time these will grow as big as the native conifers behind the houses in the last picture anyway. Not just too tall for the bed, but too wide. One I've mentioned that was bought as 'Pendula', planted at the entrance to my place shot right up and was soon hanging out over the street, left behind a stump about 18 in. across when I had it cut down awhile back.

Evergreen plants will also drop spent parts on the neighbor's lawn. And probably also shade it out more effectively than deciduous trees. So now there are two other aspects of the proposed scheme where a tall planting over along the fence may not be the optimum way to achieve the desired level of privacy. In other words if you don't want to affect the neighbor's lawn at all, including merely dropping leaves etc. on it you are simply not going to be able to have a tall hedge or screen along that fence line. It's too bad the wire fence isn't the maximum height allowed by local codes (6 ft.?). Then you could achieve a lot of screening merely by covering it with vines, such as the clematis. This approach would occupy minimal horizontal space and vigorous kinds like that develop rapidly. Even this arrangement would still produce a shadow, generate debris - and in addition would have to be pruned to keep it close to the fence - on both sides of the fence. A big part of the problem is that the neighbor's have done nothing to give themselves privacy from you, on their side of the fence. I have the same situation here. In addition I have had them reach over my similar height wire fence - I am not the one that had it installed, would have gone to the full 6 ft. height allowed if I had - and cut off part of a screening planting I had in place, throw the prunings down on my side of the fence because "it drops leaves on our bark". So I took the planting out. Now they complain about my sensor activated flood lights, which "shine in our bedroom window". Point being is if there is any possibility of similar reactions from your neighbors you again may want to instead focus on doing what you can over near where you are when you think you are too open to view, instead of over by the fence.