I am making a suggestion of how you might make the bed line and where you might put a small tree (like a crape or Vitex ... centered at the face of the side wall, where I put white lines.) Not making suggestions for what you fill the bed with, but hopefully, it will be plants that are the right height for their location. Would do away with the small circular bed (red "X".) As far as "edging" goes, a flush mowing strip (like how the curb at the street edges the outside of your yard now) looks much better than a thin vertical edge sticking up above the grade level . It should be 8" wide or better. The live oak is going to become very large. Personally, I would not want it low branched in front of my window or coming at the house, so would make sure that those low branches are removed right along as the tree gains height.

No one has responded to you in a month? Man this forum is dead! ^_^ I think herbs look good among big rocks... take at look at Lavender, Nepeta (catmint) and Agastache (hummingbird mint). If your drainage is good, you can also try succulents such as sedum, sempervivum, lewisia, etc.

I vote for 'Sky Pencil.' Everything else you mentioned wants pruning if you keep within the size you outlined. You won't be wanting trees that drop fruit or hang over the walk. Would you commit to a lifetime of pruning spirals? If it's as I visualize, you could maybe put two Sky Pencils side by side in the spaces? I'm seeing four sides of the octagon as being walkway and four alternating sides being where you're putting shrubs? A 6 foot circle with 4' wide octaganal walk around it? Total of 14' measuring across the flat sides? You're planting in 4' nooks that flare with the walk? Nell

@frankie- I like your thinking. I may consider extending the lattice fence around the bulkhead and AC unit but would still like to fill something in where that mulch bed resides. I dont want to fence the entire bed in as that part of my yard is not wide and it might not be aesthetically pleasing.