I've been reading around and I'm a bit confused now. Apparently, if you use two spell components, only the first one is actual used when the spell is cast. For instance, if I were to make a spell composed of Projectile, Frost Damage, Lightning Damage, only frost damage would be dealt if the spell were to hit a mob. Is this true? I'm a bit confused by the spell crafting system as of yet, and the wiki hasn't shed much light on that topic.
Yes, this is true. However, I think it's theoretically possible to have multiple spell effects by nesting spell shapes.
What that means is if you were to write a spell as Projectile: Frost Damage, AoE, Lightning Damage it would first shoot a projectile that does Frost Damage, and on contact produce an AoE of Lightning Damage.