depends on your area also, look up plants that are native and plant combinations of those for something that is blooming all summer and others that offer contrast in appearance to make this thy strip inviting and unusual. put some early bulbs in there and then the strip will be welcoming from early on.

I've just planted some day lilies for the first time so I've noted karemore55's advice. Thanks!
But the plants in the pic look like lomandra to me? Or maybe phormium? If the former I believe they benefit from being cut back to the ground every few years. Unless you'd prefer to get rid of them and try something else? Looking again I'm inclined to say phormium. They do look like they have potential to crowd the path. A low easy to clip shrub might be a better choice. Or if you want to keep the strappy plant style going, there are smaller varieties and varieties with a more upright habit.

To me the plants look as though they may be a mixture of New Zealand flax and native Dianellas. They do look ratty.
The garden bed, especially at the lower end is too narrow - this is one reason you are having trouble with it. It is hard to get water to stay there - it will probably all run off.
What about a hedge coming down the line of the bed? Many hedges don't need to be regularly clipped, especially many of the conical shaped lily pillies. But the bottom area isn't wide enough for these so you would need to use a different plant in the lower section. Like a Japanese Box for instance which would need clipping. They are both green and tough. There are instances where there are hedges used of different heights, and this could be one of those instances.
Your last picture shows a garden that is well cared for and looks good.
I have day lilies in my garden that I regard as weeds - I cant get rid of them they are so tenacious. I wouldn't recommend planting them.
Whatever you choose, you need to integrate this choice with the style that you have in your bottom photo, so that there is continuity. Then it will come together.
All the best
Alison

I would plant some different plants of varying colours that do no grow to large or over a metre.

A row of viburnum 'emerald lustre' would look great, lovely shiny green leaves, new growth soft peachy colour, we have a hedge of these at our front under chanticleer pears and they look beautiful and have withstood all weather conditions, fast growing , I just trim them to keep as a hedge.

Old post.