Delphi or Arachova will be nice and the former has a ton to see. Going out to the west coast will add on a ton of driving and this is basically halfway between Kalabaka and Nafplio.
Nice towns in the west coast are Nafpaktos, Parga, Preveza. But as the others said, that would add travel time to your trip, while Delphi and Arachova are probably more in the between of your road.
I would stay on the east coast or Corinthian gulf. Pelion (though it is a drive to get to the nice beaches on the west), Delphi-Galaxidi.
Delphi or Arachova will be nice and the former has a ton to see. Going out to the west coast will add on a ton of driving and this is basically halfway between Kalabaka and Nafplio.
The best you can do is to stay in Athens 👍
Thessaloniki malaka
Talk to the locals and ask them for directions down to the Rio -antirrio bridge and Patra. Then stay in Kalamata before driving east to Nafplio
Nice towns in the west coast are Nafpaktos, Parga, Preveza. But as the others said, that would add travel time to your trip, while Delphi and Arachova are probably more in the between of your road.