Im interested in moving over to real plants and was considering starting with some Vallisneria but im worried my substrate isnt deep enough, how deep should it be for this plant?

Another thing I should ask is which species of Vallisneria would be best in a tank with a water depth of 16 inches? I was going to go for Vallisneria Spiralis Straight Vallis for the background but it seems this grows to over 23 inches?

And I guess Vallisneria tortifolia would be what id want for the front?