Lavender won't get anywhere close to the height you need although a great drought tolerant plant for other areas. Some choices: Euryops Leptospermum (tea tree) Lycianthes rantonnei (the blue potato bush) Arbutus unedo 'Compacta' (dwarf strawberry tree) ceanothus - California lilac And you can always check out your local nursery/garden center. They should have a great selection of waterwise flowering shrubs to fit the bill.

I'd definitely avoid Ficus - their roots can be VERY invasive. Depending on what/who is on the other side of the fence, you might need a very narrow tree so it doesn't shade your neighbor's yard. One good choice for a narrow evergree tree (depending on where you live) is Radermachera sinica (China Doll Tree). I've had friends grow this with success for privacy in a narrow side alley. If you can have a wider tree, say 15-20' wide, I'd suggest Calliandra surinamensis (Surinam Powderpuff Tree), which blooms every day of the year (at least in my area) and looks a lot like Mimosa but WITHOUT the problems of messy pods and self-seeding. Another possibility is Agonis flexuosa (Peppermint willow tree). To learn about lots of other trees I recommend the book "Ornamental Trees for Mediterranean Climates: The Trees of San Diego," published by the San Diego Horticultural Society. It has over 500 photos of 260 trees that do well almost everywhere in So. Calif. with lots of info and an handy chart. Here is a link that might be useful: San Diego Horticultural Society

This is my star jasmine. Grows like crazy after the first year or two. Wonderful fragrant flowers in the spring. It's growing on a four foot chain link fence on right. Covers it completely.

Without a general location (GA zone 7 is different than Cape Cod zone 7 or WA zone 7) panicled hydrangeas like those you listed will do the best in zone 7 with much sun of the various hydrangea species. Most of the other hydrangea species need afternoon shade or all day dappled shade since they naturally grow in the understory and are much needier of constant moisture. I love panicled hydrangeas, and in my cold zone 5 they color up well. Fom what I have read they may not do that in zone 7 unless you have cool late summer and fall evenings and nights. In your case, I would ask around to see how they behave in your area. If they don’t color well and just go from white to tan without the late summer reds, consider a type where the fall pink tones aren’t a big part of the appeal like Limelight or Little Lime which are both lime green and white, or White Diamond that stays very white almost until frost here. In the area where you have the box, I would remove the landscape cloth under it. That will allow the plants’ roots to grow into the soil under the boxes. The hardware cloth and gravel won’t be an issue for the roots, but the landscape cloth will interfere with movement of water and any deeper roots. And IME gardening in an area where voles are a constant issue, they don‘t seem to bother panicled hydrangeas at all. I have 5 of them in several gardens where other more succeptible plants have been killed while the hydrangeas have flourished.