Open World vs Hexagonal Grid mode (only standalone and viewport modes)
In Open World mode, all path-finding functions use an internal / invisible matrix of 2048×1024 map positions to compute terrain features (land/water), elevation, blocking status and crossing cost. In this mode, no visible grid is usually used (although it can be enabled).
In Hexagonal Grid mode, in addition to a visible hexagonal grid, the path finding methods are specific to the hexagonal cells. Each cell contains a terrain feature (land/water), blocking status and a different crossing cost per hexagonal edge.
The Path-finding section in WMSK inspector let you assign a heightmap (a grayscale texture) and a water level which is a value in the 0-255 range that determines where’s water and where’s land. Any color value below the water level in the heightmap is considered water.
There’s no global switch to choose one or another mode. It just depends on the API functions you use.