If Titania did die, then would Lily or Ella become Queen and be in control of the drones?

Yes, I think Lily and Ella would try to work together for a time, although it’s probably pretty much inevitable they’d end up fighting each other without their Queen to unite them.  Obviously most would want Lily to win that fight since she’s not as needlessly cruel and other people would have a better chance of being able to reason with her.  Whereas Ella is completely ruthless and ever so slightly mad.