Tips for building terrain

Hello, I’m in the process of building a massive world for a game of mine, and I want to make the type of design such as Arcane Odyssey, the sort of retro design, with a modern twist, how should I go about this, parts in studio? Models in blender? What would be the “best” way to do this? I do want to make a seem less world like lets say a beach with an incline, ect.

Any and all help is heavily appreciated. It’s my first doing something of a magnitude as shch.