Just to add more confusion 😵💫🤪
I agree with @Tony s (and Cory), gravel is better. But small gravel, like Flourite size pea gravel. It does not have to be Flourite though, just any smaller sized gravel because the plants will have an easier time rooting in it.
You could also just get some small terracotta pots and plant in those then bury them in your existing substrate too instead of changing out all the substrate. BUT it will almost certainly look better and give better growth of large plants like swords if you just change out all the gravel.
Also, you need at least two inches of depth for ease of planting and root development.
HTH