The "basic" neon tetra is Paracheirodon innesi. Paracheirodon simulans is sometimes called the false neon, or the green neon tetra. Cardinals are a completely different species also. That said, many people have cards and neons that will shoal up together. They are closely related and they will generally be fine together. Typically though, most fish really school best with the8ir own species. Neons and cards are of the more common exceptions. Still, I would just stick a nice big group of the same species.
Two roads diverged in a yellow wood, but thankfully they both led to fish stores.