You can’t compare the Akuapem Paramountcy to Asanteman’s Chieftaincy. The Okuapehene is equivalent to a Paramount Chief like the Mamponghene or Juabenhene.
The Constitution states The Asantehene and other Paramount Chiefs. He is the head of a Confederacy. He may not be ruling a kingdom but he is the only Traditional Ruler in Ghana with Paramount Chiefs (66 or so) as his subjects.