Plant materials include 'Smaragd' arborvitae (less likely to split with winter snowloads with their strong central leaders), amur maple (great as a small understory tree, with brilliant red and orange fall color), magnolia virginiana (lovely pale yellow flowers, back there in the corner behind Manuel) and lots of grasses and different sedums. Everything is drought tolerant and easy to maintain.
Perennials along the west side include helianthus, eupatorium 'Gateway,' perovskia, amsonia hubrichtii, and leucanthemum 'Becky.'
If you have a professional landscape installed and care for it yourself or have a third party care for it regularly, consider having the designer back now and again to regroup. Especially if your designer is a little OCD, like me :)
This is not the best shot, as it's out the window, through a screen, with a phone. BUT, now you can see the whole layout, with the flagstones at strategic locations. You can see how the flow between deck and ground level works.
The hemlocks will eventually grow quite large, creating a real sense of privacy, enclosure and tranquility.