Scalare - I'm sure you know that they look like
Altum - Body covered in more % brown stripes than silver base. Deeper body, reach about a foot in height, more upward pointed snout. Fins are typically 'thinner'
Leopoldi - (LFS has some selling for $30, 100% real ones) Some have red spots on body. Also a black spot where under dorsal fin. More elongate body. Has a metallic-blue spot on gill cover. The only angel with a slightly downward pointed snout.
These are the 3 basic ones. Then you move into Peruvian Altums and whatnot.