As a practical matter, to level the right side, you'd need any large "planter" or retaining wall to be 4-sided; to be impervious to moisture and to keep the soil from falling through the lattice into the storage area as well as preventing the rotting out of the stairway arrangement. Many plants are zone dependent, and you didn't note yours. If barberry isn't an invasive where you are, the green tinged with red is a good color choice. Prickly yes, but very largely deer proof. Deer might taste ninebarks, but they're vigorous growers and can outpace a nibbling. Our winter has been hard on the deer - and I usually get plenty of them - the last I saw them a couple of weeks ago, they were trying to eat spruce. So they're desperate now with 3-4 feet of snow cover and natural food scarce. With such a grade as you have, it might be difficult to make up for it with plantings - but maybe an island away from the house with an arrangement of conifers would move the eye away from all the lattice on the right side. Spruce is "normally" reliably deer-proof, same for any conifer with short spikey needles. A smaller island on the right with a focal point conifer or shrub with perennials - deer won't touch (even if starving) the salvias, Russian sages, nepetas , peonies.

First, let me say that I wish everyone who offered a picture of their property would start out with a picture such as you have used. It shows the wide view. It's reasonably sharp and decently lit so details can be seen. While other pictures might be needed as the thread goes on, this is the headline picture that best explains to the person who's never been there what the property is about. So good job on that! With landscaping, things generally look good when first they make functional sense. A quick way to make things look odd is to impose things in the landscape that seem to serve no genuine purpose ... like retaining walls where there is no reason to retain additional earth. If you really want a nice landscape, I think it is setting out on the wrong foot to say you like this or that without first thinking of what the house and property is saying it needs and wants. The front door sits low to the ground. Is there any reason to raise the elevation anywhere in front of the house? To me, it looks like there is not, and that has me believing that anything like a raised garden bed with rock walls in front of the house will seem like a bad idea. It looks like you have a swale at the right side with the grade falling off and an existing retaining wall at a level that makes sense. Retaining the earth against the house allow you to level out the base which is holding up the building and give the house a setting that looks more stable than a slope would provide. But the planting space this retained area creates seems pinched and far from able to provide a luxuriant looking setting. If you want to display and feature something (like the face of your house) then don't use plantings to pinch and smother it. Use vegetation AROUND AND OUTSIDE OF IT to help make sure that the house remains the center of attention. Let those plantings guide (as like a [wide] funnel) one's view to the house. You could rebuild the retained area in a larger configuration, or leave it alone and add plantings outside of it in a larger configuration. You should say where you're located if you want people to also give you actual plant suggestions.

If you don't get much water, I would concentrate all your water-loving plants up by the house. There are some gals on the Antique Rose forum that live in Southern California...and they grow beautiful roses, along with many other plants. You might want to try that forum, too :) It would help if you say which direction the house faces, so we know if it's sun all day, partial shade, etc. An east facing garden is very different from a west facing garden. Our front gardens face southeast, so the afternoon shade is a huge benefit, when it 90+ degrees outside!

New windows can help with noise if they are chosen with that in mind. Plants can provide visual buffer but do not buffer sound, even with density. I hear traffic despite being more than a half mile through dense woodland in either direction from highways. The only thing that will buffer road sound is something solid like a wall or solid fence, neither of which would look particularly appropriate in your setting. If you want the visual barrier to be year round it will need to be either an untrimmed fountain shaped and densely twiggy plant like forsythia or ninebark, or else evergreens like Rhododendrons or shrub sized conifers. Depending on the look you want, you can use a mix of several types of plants for a less formal look, or all the same kind for a more formal look. Look at large shrubs as opposed to trees because of the power lines. Good on you for thinking of that issue as many folks don’t. I don’t know what you mean by a boulder garden, but generally in the eastern half of the US, rocks are difficult to keep weeded. They tend to do better in areas that are more arid. Considering that grass appears to grow well in your area, it isn’t a choice I would be likely to make. Can you provide a photo of what you were considering? While growing zone is one helpful piece of info in making plant suggestions, eneral location is as well (nearest big city and state). For instance, there are parts of MA, WA, VA and NM that are in zone 7, but due to different climate, moisture, and soils, different plants will grow well. Is it full sun without the trees or are there some along the edges that aren’t visible in the photo?