The snails you refer to are Malaysian Livebearing snails; they will burrow through the substrate and are a good addition in a planted aquarium. Terraces are easy to arrange with rock or bogwood.
Live plants in aquaria with suitable fish are important as a major source of filtration. The type of plants that will grow well in your aquarium depends upon your light. Plants need adequate light (intensity and duration) and nutrients to grow, and different plants have different requirements. "Nutrients" includes carbon dioxide (CO2), macro nutrients and micro-nutrients which are minerals; CO2 comes from the fish [or adding a CO2 system] and some minerals come in the water but others have to be added through liquid fertilizers. The most important thing is the light.
With 1-2 watts of full spectrum light per gallon you will have good success with rooted plants (Echinodorus, Cryptocoryne, Vallisneria, Sagitarria, etc.), Anubias
, Jave Fern, Ceratopteris floating, and some of the stem plants. With more light (4+ watts per gallon) you will see faster growth and stem plants will thrive, but added CO2 will probably be required to balance. What type of light do you have [type, wattage, number of tubes, etc]?