The map can be generated by Procedural generation but it's possible to plan IA with auto learning based on rating system to generate each time better map.
The normal Heightmap algorithm do a very curved Heightmap. But to maximize the compression and keep the correct style of the map you need drop the curved style.
In mathematics, a Voronoi diagram is a partitioning of a plane into regions based on distance to points in a specific subset of the plane. That set of points (called seeds, sites, or generators) is specified beforehand, and for each seed there is a corresponding region consisting of all points closer to that seed than to any other. These regions are called Voronoi cells. The Voronoi diagram of a set of points is dual to its Delaunay triangulation. Wikipedia
After you need pixelise it to use it into tile, you can use 1 tile, 2 tile step (or more).
Transition and height
Do the transition border into the zone only do gap between zone.
Based on mask, terrain spot, altitude line like into map.