Plantings along the sidewalk might make it look even narrower. Especially if the plants are tall, or sprawl onto the sidewalk.

Agree with littlebug. Could you afford to add a paver border or something to the existing walk? Even that would help.

I would probably go out to where the curved bit at the base of your stairs and your planters are - any wider and you'd have to add something to widen those curved pieces. How wide is the current walkway in inches?

Yeah, 30" is way too narrow for two people to walk side by side - you'd want at least 48" for that. I think having it the same as the width at the top would look great, and with 66" you could plant beside it and not worry about your plants taking up too much room if they flopped over the walk a bit.

I don't know anything about your weather but the area looks like it gets plenty of sun. How much futzing do you want to do? Are you willing to plant annuals each year, or would you rather have lower-maintenance perennials? Whatever you choose, I would keep plantings relatively low (maybe under a foot) so as not to visually crowd the walk.

Can you post another photo, and include the entire house from the front. I am ok with the narrow walk if you do not have border along the walk. The border forces you to stay on the walk and if for any reason the plants overflow - the walk space becomes more limited.

If you do not intend to widen the walkway - by far the most appropriate suggestion yet offered - then fill in the gaps between it and the lawn and let the lawn grow up next to the walk. Having that empty stretch is a trip or sprained ankle waiting to happen - 30" is extremely tight even for a single individual to walk along. And planting alongside that narrow a walkway is just too restrictive and crowding.

I realize that you aren't liking this advice, but as others have said, widening the walkway would be your absolute best investment. Plants for that length of walkway would waste money you could use to really add to the look of the yard IMO. Use 8"-12" patio block with the longest dimension running perpendicular to the length of the walkway on both sides to give you an extra 16"-24" of width. Remove the soil to the depth of the blocks and save it for use elsewhere, tamp down the subsoil firmly, and inset the block to the depth of the walkway using sand to level as needed. There is patio block dyed to look the color of brick at considerably less cost. Since you don't have frost, you can most likely get away with this rather casual type of install, though a deeper base of sand or crushed gravel with fines included would be better. You can look up how to install block, but I have found that my patio block installed on gravely soil hasn't moved at all despite having frost. My block is 2' squares and 8" rectangles. Take the time to price out patio block for that length of walk vs. what you would have to spend for plants to fill that space and compare.

Next I would make the bed in front of the house deeper front to back, so that it comes out as far as the base of the steps at a minimum. Right now it looks crowded and pinched. At some point you will want to replace the shrubs since they are tight against the house and look to need frequent pruning to keep them at that size, but as long as you are willing to prune, this doesn't need to be done right away. Plant your flowers at the front of this bed rather than along the walk. Replace the smaller pots on the knee wall by the front steps with taller pots set on the ground just outside the kneewall. That will give the look of a wider front entry. Your current pot placement tends to narrow the entry.

Are the plants along the fence on right side of the yard yours or your neighbor's? If they are yours, there currently seem to be many different textures, but not in a particularly attractive way. I don't know Louisiana plants at all, but some vines that will stay relatively small and are all the same will give it more coherence and can climb the fence. Alternatively, fasten bamboo matting framed with stained wood to the fence to give a more polished look. Not sure what is on the other side of the house.

Do you like the azalea that is in the yard? If so, look around for ones you find attractively shaped and read up some about pruning before tackling it. Cut individual branches with a sharp pruner rather than using hedge shears. I like azaleas, but that one seems overgrown. IME they take well to pruning if done well, and right after bloom is the best time to prune if you want bloom next season. If you don't like it, start researching plants to replace it, small trees or large shrubs that can be pruned to tree form. Don't remove it until you have funds and an idea in mind to replace it.

Long term consider if a picket fence with a gate surrounded with a perennial garden would be something you might like across the front of the yard. It would add considerable maintenance, so if you don't want that, skip this.

In all honesty I most likely wouldn't put roses that had any thorns near the front steps. I know nothing about whether Knockouts have thorns and have no experience of with them as to size, growth habit, etc., but a plant of limited size that won't sprawl into the path and steps would be fine.

You want to cut back the azalea right after bloom. They form flower buds over the course of the summer, so if you wait until fall you will remove next year's blooms. It will look a bit naked for a bit after a hard prune, but it will form buds along the stems and put out new leaves in a few weeks.