Smithing perks allow you two things:
Forging weapons/armor of a certain type
Improving those weapons beyond what you'd usually be able to do.
So getting Steel Smithing and Arcane Enchanter would allow you to make Steel equipment and improve any enchanted gear you may find. You'd only be able to smith Steel and the basic stuff (leather, iron, etc.) but you could still improve any and all types of gear you find, just not as much as you would Steel.