Congratulations on your new interest in gardening and on working up a plan before planting begins; it's an important first step. Please describe some of the dimensions to help determine if the plant choices and placement are appropriate. This overhead view is useful, and an elevation view will also be useful, whether a photo of the area or a drawing. You'll probably get lots of questions during this process, please be patient. As to the mulch question, my personal preference is for organic material. Many cities have greenwaste recycling where you can pick up a truckload of mulch free -- check into it.

Judging by the landscaper's list, I'd say he or she assessed this area as relatively hot and dry. Also, that slope is a major consideration in terms of the ability of the plants to hold on to the soil and survive erosion. I also think you will not be climbing out onto that hill for much maintenance. Given those thoughts, I think several of those choices make sense....the low juniper is actually a very good idea there, the nepata and the coreopsis as well. The barberry is actually a tough plant that would do well there, however, even the crimson pygmy is considered to be invasive plant and should be avoided. So, it's good you don't really like it. (Sadly, I'm fond of it, but can't use it in good conscience.) If you do use the Miss Kim, I'd put them at the top or the bottom of the slope....I'd feel nervous about their ability to hang onto the steep part of the slope. You might also consider a purple sand cherry. I also think the boxwood along the stairs are a nice idea for framing the area. For trailing over the top of the wall you could do some creeping phlox, and/or the wonderful Homestead Purple verbena. Just some thoughts.

Sarah, You can utilize the bushes now that are already in the "shady" bed that you want a japanese maple in, by the way, I think it would be a beautiful focal point there. Good idea! Hydrangreas are nice to grow with them, and you can look online to see some shady garden ideas for the maple, but I would make it my focus. The plants on the other side of the steps, what are they? Is that a holly at the corner of the house? Does it stay ever green? It's a nice size, and if you buy something small it will take many years to grow in the way you want it to look. If its not a holly, a beautiful emerald green arborvatie would look nice there. They aren't real expensive either to buy a good size 6 or 7 footer for that corner, and they stay bright gorgeous green all winter. I have one, I put it right on the corner of my house, but it was really small when I planted it and it isn't even 5 ft tall yet ugh. Indian Hawthorne, an under planted shrub that is easy to prune if necessary, is also a shrub you sould look up online. They are not hard to care for, and flower in spring for about a month. They "play well" with others, LOL and they are evergreen. You should consider them. Albelia, a shrub that is evergreen, prunes easy, fragrant pretty flowers through out the summer, I have "Kaleidoscope", the leaves are 3 colors, you should look that up online, you will have to prune when you feel its getting too big, but I only prune the one I have once a year. That's not too bad considering I have color in the winter. Gardenia that is hardy to your area would look nice in that alcove. "Chuck Hayes" is very hardy, down to zone 6. Evergreen, just needs a little compost and pine mulch, and requires about the same water as your jap. maple. FOr the corner of your garage area, at the end of the house, you might want to look at Evergreen Dogwood tree. They had them at the nursery this year, I have not seen one yet growing in landscaping, but they are new and bloom really nice in the spring. Just another suggestion for that corner. I have a sweetbay magnolia. I absolutely love it, though it is pretty young. I have it growing in full sun, and I water it alot, and it has bloomed this summer, which I was thrilled about. But, it will get big. I have seen pics online, and they will grow tall. I need it for the shade, I have very little, and I planted it really close to my driveway, but I will trim it if I have to. I really just wanted to give you a few suggestions as to what plants I already have that are evergreen and I appreciate in the cold months when there are no leaves. Good Luck to you.

the buds are there in fall .. tiny .. but recognizable ... so any severe winter.. can destroy them ... if its a regular old L.. its way too close to the house .. when the time comes.. look into 'rejuvenation pruning of flowering shrubs' but your comment that they havent grown much.. makes me wonder if it could be a dwarf.. like pallidin ...Syringa meyeri 'Palibin' .. but that would not fit with gals vulgaris suggestion ... ken https://www.google.com/search?q=Syringa+meyeri+%27Palibin%27&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjK17GvtonMAhXD5yYKHTRYDR0Q_AUICCgC&biw=1187&bih=745&dpr=0.9