Where will the perforated pipe discharge or will it? Also, what is the angle of the slope? I'm not a big fan of the weed blocking fabric but it can be useful here and there. Weeds will get into it though and then be harder to get out. You don't want trees and shrubs right next to your trench since their roots can invade over time. Appropriate grass seed covered by an erosion control blanket might be one option. Terracing the slope is another option. Deep rooting plants is yet another option.

Timber when done right can last, but there are also block walls that are only slightly more depending on the block and more reliable in the long run. Hope this helps!

I am located in Northern Virginia, which I believe is zone 7. Here is a view from the "walking trail" looking up at my backyard. This is from the perspective on the other side of the black fence. and another pic. I obviously cant remove the black fence and the retaining wall with the huge 6 foot drop for safety reasons, but id like to atleast partially hide it when standing in my backyard with small trees/schrubs/bushes etc. If i can hide the black fence from view when standing up in my backyard, and hide the 2nd retaining wall, while not obstructing the view of the walking trail, that would be a win.

Rather than write a whole bunch, I am going to give you a couple of links to threads where folks asked similar questions. I showed one of my large shrub borders and talked about how I thought about arranging it as well as many of the plants I used. While mine isn't along a fence line, it has a similar function of providing separation from one area to another. I didn't find a whole lot on the web that addressed what I saw in my mind when I wanted to do this, and local nurseries just suggested I put in a line of arborvitae which would look silly in my rural area, so I've added photos that show it in various stages. By now it's been in place 8 growing seasons and I am starting to look at editing it a bit more than I have so far. Mine is a bit taller and wider than your intentions, and it is in a colder zone and a bit sunnier. But many of the same plants will work for you. Feel free to ask questions. Several comments including a bunch of photos further down the thread here: https://www.gardenweb.com/discussions/3113384/shrubs-for-privacy-along-a-fence?n=22 I'm including this link mostly for my third comment about how to arrange repetition so it doesn't look too random: [https://www.houzz.com/discussions/landscaping-renovation-needed-along-fence-line-dsvw-vd~5260700?n=14[(https://www.houzz.com/discussions/landscaping-renovation-needed-along-fence-line-dsvw-vd~5260700?n=14) Repetition of some of the plants in mid-autumn: Rhododendron Olga Mezitt and Amsonia hubrichtii are smaller and so toward the front, and taller deciduous spicebush/Lindera benzoin turning gold in the middle ground. The two evergreen Thuja/arborvitae here are repeated elsewhere in the bed, just not in this photo as are most of the other plants in this view. Here is a similar view in spring And this view shows how well it blocks sight lines to the work area behind it after 5 years, even in winter with just the evergreens and whatever remains on the deciduous plants.