There is a retaining wall about 40 feet long and drainage is good.

I have no personal experience, but I’ve read that pool owners vastly prefer things that do not shed leaves, seed pods, or flowers.

Go with a native species. Much easier to establish and care for and less vulnerable to climate and weather issues. I'd suggest Pacific wax myrtle, Morella californica. Evergreen, very prunable (can be hedged formally if you prefer) and not particularly messy, although it should be noted that any plant will shed leaves, flowers and any fruits/seeds from time to time.

One of the best screening plants for the West Coast.