Given that floaters typically sit just inches (or less) away from light bars, pretty much any of 'em will likely do well. I'm partial to red root floaters in high light conditions given their color, lovely tiny flowers when they bloom as well, but any of the salvinia would likely do well too. Frogbit's always done better for me under moderate lighting, but I've certainly seen it used in high light tanks.
I suspect your water lettuce failed more due to the change in conditions than light levels--I've dwarf water lettuce thriving in 10+hours of direct sun in a tiny vase out on my patio (in Arizona!) and the it's happy as can be despite having no water flow and daytime water temps in the high 90's--and more doing equally well (if slightly smaller and thinner leaved) in a water barrel in full shade.