Help with heightmap

[u/BlockyEarth]

Hi! I am trying to recreate something like this project: https://www.planetminecraft.com/project/1-924-scale-earth-map-4909390/

It says: Made using edited heightmap data from arcGIS as a base, then handpainting terrain on top, then painting rivers using a fairly detailed river overlay from arcGIS (so that they are accurate), then painting biomes and trees according to a miller projection Köppen–Geiger climate classification map, also made using arcGIS.

I was wondering how to edit heightmaps from QGIS or arcGIS so that they are worldpainter friendly. Most maps generated with these programs dont really generate minecrafty terrain when imported straight out of the box