Might I recommend Romancing SaGa 3 and SaGa Scarlet Grace Ambitions? Both of these games involve non-linear, open world explorations. As for combat, they are turn-based, so I'm not sure if that's what you would consider a "good" combat system. Also, unlike traditional RPGs, which use a point-based system to level up and gain new skills, SaGa games involve a "Spark" system, where new techniques are learned randomly or through use of an existing technique during battles.