L128 (blue phantom) is more omnivore while "Royal Pleco" are more vegetarian. If fed mostly vegetarian diet, both will do fine. L128 will do fine with the veggies for both also picking up after other fish. Consider using something more nutritious and taking longer time to break down than zucchini, like pumpkin and sweet potatos.
Driftwood is much more important to "royal pleco" than L128. If you do add a "royal pleco", keep your eyes on the filter material to see if there are wood shavings/dust on them. If not, change to a different type. Some "royal pleco" may consider monapi driftwood a little too hard.
Do keep in mind, pretty much all types of "royal pleco" will reach 18" easy, some will go well over 24"