Welcome to the forum.
The primary benefit of marginals for water quality is the nutrients they take out of the water leading to better water conditions and less chance of algae growing. None are oxygenators that I know of in the sense of adding it to the pond like the submerged bunch plants.
Keep in mind, submerged oxygenating plants will also reduce/use the oxygen in the water at night or on very cloudy days when not photosynthesizing.