I wish I could give you some advice but since we are from very different parts of the country the plants I know wouldn't be of use to you, like palm trees and Lantana.

Very hard to see details, but if the minimal amount of planting space is accurate, it looks like you have no more room than to plant some colorful annuals or perennials, mixing or not as you u see fit.

Prairie grasses are as low maintenance as you can go. Look for Karl Foerster or variety of Maiden grass.

Around a pool, you want something that will not lose its foliage (ie drop into the pool) and low-maintenance. im in the northeast and have a row of white Annabelle hydrangeas as a hedge around the pool. You could try that, or a row of smaller white Bobo or Little Lime hydrangeas.

It does not make sense to take what is a more or less narrow planting strip and divide it in half with the concrete "curb." I would remove that and make two adjacent skinny strips into a wider one, from the pool deck edge to the fence. If the concrete barrier is a bed edge -- in that it's keeping roots in check, I'd relocate it to the perimeter, abutting the fence. Some of the grasses mentioned may get quite large, so I wouldn't create a hedge out of them, but use one or two here or there as "punctuation." The same is going to be true for most shrubs, which will want to exceed the area. Still, I don't see where you stated your location, so no one will know what grows where you are. Generally, I'm thinking taller things near the bed run ends and shorter toward its center. At the tree might be an exception to that arrangement. You also might need to limb up the tree a little to get it over people's heads. Perennials, especially long blooming ones, seem like they would be useful to you. Daylilies would be one. Russian sage might be somewhere. Return with a location.

The next step after you hear ideas about what you could do, is to convert the yard into a PLAN, where basic elements are accurately drawn on paper, as if a simple map. That's how you will know how many plants will fit and where they should go.