Waterfaller, the plant on the left is the windelov, a variety of fern (Microsorum pteropus 'Windelov'). It's a very hardy plant and it gets quite thick given good conditions.
I like the longer dimension of a 20L. Mine's a 20H. I didn't know about the 20L when I got my tank. I think the 20L is definitely better for aquascaping.