Is this a 18-electron aromatic system?
No, because as the OP says in the question, the rings are not in a single plane.
Is this compound considered aromatic?
Yes, because it has three aromatic rings, as the OP stated. They all have 6 delocalized electrons, so they conform to the $4n + 2$ rule.
"What if" all carbon atoms were in a plane?
The C14 and ...