Zone, location? what way is north on your drawing? In my experience, decomposed granite is good for paths only. I like mulch for around plants because it eventually enriches the soil, and keeps their roots cooler in the meantime. River rocks can be pretty but I haven't found it to be less maintenance than mulch -- weeds and seedlings will germinate and have to be pulled before they get too big. It's as easy to pull weeds from a nice layer of mulch as it is to pull them from pebbles. But my experience is limited, so it will be interesting to hear from others.

I wanted to expound a bit. We have no information about how you came to work with this landscape architect. The way it should have happened is that you became aware of her work, and the way she solved landscape problems, and hired her on the basis that she would use the same good judgement in solving your landscape problems. And then not second-guess that her solutions were faulty -- based on some less experienced person's opinion, or that of many people. It should not have happened that you little knew or understood her work and decided to blindly throw money at your problems, figuring that any pro would solve them in a satisfactory way, that you liked. Within the scope of landscape design, there are radically different approaches by different designers. If you were to peruse this forum for awhile, you'd see how different the solutions and opinions can be. One of my consistent complaints about designers, especially new designers, is their propensity to use too many plants. The tendency to do this is driven, and driven hard, by several factors that will probably continue for all time, since they are embedded in the industry itself. One of those factors is that everyone in the industry likes it when plants are sold. The more that are sold, the better. The more plants there are, the more the job cost, making everyone happy. Even the owners believe they have achieved a higher status if they have spent more on plants. The owners also have an expectation that more plants equal a better job. Designers often believe it, too, and even if they don't, they second-guess that it is the owners perception, and therefore the feel pressured to use more plants. It's circular maelstrom that will not likely end anytime soon. Personally, I have recoiled in almost the opposite direction, thinking that simple form is superior to quantity and complexity. Yet, it is apparent that the majority, or at least a great many people reacting to my suggestions, think that the result is boring. However, as a retired person, I am immune to fad ideas, regardless of their popularity. I have not taken a fine tooth comb to your plan. Actually, I have not looked at what the plants are. That's too much eye strain for me! But the overall impression is that the yard will be swamped with plants and house will be engulfed by them. You have to decide if this is the general direction you want go. It it is, then by all means, have at it. But if you don't, here are some simple suggestions for eliminating some of the plants, primarily by redefining bedlines. I would not call these suggestions-that-are-carefully-worked-out, but they are a first stab at reorganizing with the thought of simplifying and scaling down the quantity. (BTW, I had to laugh that, in the original plan, the trees at the street appear to be planted along the center of the city walkway. It's going to be hard to pull that off! ;-) [Also BTW and FWIW, the decision to use so many plants is one that should have been ironed out early on at the schematic or concept stage of the design. Maybe it was and is what's desired. We don't really know. But if it's not, then it should have been nipped early in the bud. Just sayin']

Planting under a tree is tricky and often impossible with potted material. Sometimes once can dig a hole for a 2" pot, sometimes the best one can do it install root pieces and wait for them to grow. Hostas could work that way. Or consider another groundcover. It's definitely not a place for turf. It would be good to redefine the bedline such that it encircles the tree rather than coming close to it as it does now. The circle should be proportionate to the tree's size and be a perfect circle, so as to look completely intentional, with the tree being the center point. The linear potion of the bed looks fine but over time you might discover that it's a bit shallow. A good minimum depth (front to back) is 6'. If bed will enclose the whole back yard, it will be sizable. You'll need some groundcover that fills in any bare spots. See what's growing in your locale that can work out for you. If you can get some started, it can be a source for propagation of much more so as to hold down costs.

As I don’t know your front yard sun exposure or your location planting zone I cannot make any specific recommendations. The characteristics I would look for in a front yard shrub for that location & considering the features of front of your house are these: evergreen, flowering - specifically white flowers & mature height not much more than 5 - 6’ high & wide or easily maintained to that size. I can‘t really tell how much space you have at that corner. Here’s a link to a strurdy plant that grows well in my area & has 4 season interest. Pieris japonica variegated I think it’s important to consider colors of plants against the colors of house for front yards which is why I suggest white flowers. Pinks & reds in flowers & leaves would be lost against the pretty brick. Since it’s not right at front door whether it’s evergreen or not is less important & expands your options for white spring-summer flowering shrubs. About the pencil holly, be aware, if you‘re not already, that there are several kinds. While they’re all classed as narrow, some at maturity can be 6’ plus. The narrowest is ‘ Dwarf Pagoda’ at @ 2’ but it’s also the shortest. Google Japanese Holly / pencil holly to see the varieties. Or, maybe you planted the 2 you have & know their specific variety?