Answer: When you plan a flower bed, you need to start with a scale drawing of the square footage to be planted along with a clear idea of the purpose of the planting. When doing a foundation planting you also need to sketch out the location of your doors and windows and show the maximum allowable height for the plants before blocking the window views.
Then you need to analyze the growing conditions in that location -- sun vs. shade, soil type, soil moisture, amount of wind, and so on. This will help you identify plants that will thrive in your planting area. Next, determine how much maintenance you are able and willing to provide your plants.
Working from your measurements you would determine how much space you have, where a tree would fit, where a shrub would fit, where you would like an evergreen, where a flowering plant would be most appreciated, and so on. It can be helpful to check the view from much-used windows and from favorite sitting areas to help guide your aesthetic choices. Finally, at the end of the process, you would select specific plants for each purpose from among those that you know will thrive in that location.
It is somewhat customary to use four season interest "foundation shrubs" along the foundation of a building, but perennials can also be grown there to great effect, and they can certainly be combined. As part of your planning, you need to check the mature sizes of the plants you are considering; the arborvitae grows 4 feet wide and 15 feet tall for example so it might not be in the right scale for a flower bed. If you planted just one of everything on your lists, allowing space for each plant to mature, you would probably exceed the 50 foot length. So you may need to pare down your selection a bit.
I also notice that some plants on your list such as the barberries are tolerant of hot sun and well drained to dry conditions (typical of a western exposure with that baking hot afternoon sun) while some such as the Shamrock holly (Ilex glabra), the magnolia, the camellia and the viburnum for example would really prefere an evenly moist, acidic, organic and humusy soil and might be better suited to an eastern exposure.
Among the perennials, you also need to keep in mind that some require shade (hosta and ferns will tolerate a little gentle morning sun but can not withstand hot afternoon sun) and others require sun (daylilies) and sedums in particular do great with afternoon-only sun.
Plant selection for such a big project is somewhat complex so I would strongly suggest you work with your local professional nursery staff to analyze the growing conditions where you want to put this flower bed and then select the plants you like best from among those that will thrive there. Also make sure they will fit the space rather than overgrow it when they mature. I hope this helps.
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