——They were known among themselves as the Catuvallani (the people of the cat), the Damnoni, the Epidii (the people of the horse), the Veniconea, the Novantae, the Caerini (the sheep folk), the Smertae (the smeared people) ——
Hmmm... the names given appear to be greek in origin
I suspect there weren’t really very many picts and they were simply gradually invaded, intermingled and just absorbed into the superior culture.
DNA studies cannot find a 'Pict' gene...they're the same as everyone else.
It looks like their differences were just cultural.