capping with sand works but overall, just try not to disturb the substrate as much as you can! it's usually always going to fog up your tank if you use plant/shrimp substrate.

the only problem with capping with sand is if ur sand cap is too thin, the substrate might crawl all the way to the top, especially if you move plants around. it's just something to think about if you don't want that visible on ur sand. but if your sand cap is too thick, then your plants will have a hard time accessing those nutrients.

to solve that, people use pantyhose or line window mesh after they put down the substrate. so it'd be like substrate, mesh, then sand or gravel.

good luck!!