How to create a world map?

How can I design the world map like in Hoi4, EU4 games? I want to develop a simple strategy history game but I have no idea what to do. Should I create the map from outside or from within unity? I’m really clueless.

You could use Unity Terrain Component or build your own map from a 3d modeling software like blender.

Performance wise, I think using unity built-in Terrain Component will be better as it is optimised by unity itself.

For trees, you can use the tree editor to create your own trees or model a tree in another software and “paint” the tree on the terrain

For structures like buildings, there’s a package called pro builder you can install from the package manager, it doesn’t auto-generate buildings but you can place blocks like door, stairs or even curved stairs

I’m also currently working on my own game and I’m not really considering performance for now, so I’m learning how to use blender for a more customizable map

WHY NOT USE BOTH

Unity Terrain editor for cliffs, mountain, trees

and

A 3d modeling software for buildings and other complicated structures

NOTE: unity 2022.2 has a new water system that can be used to create pools, oceans, rivers e.t.c.