The general method that I have been using is to make the approximate landscape using the method that I shown which gives a very smooth undulating DEM with no detail in it and then take real earth DEM data from the Space Shuttle missions from NASA (the SRTM data) and flatten that so it has loads of detail and no undulating height information in it. Then I add on the flattened detailed SRTM data on top of my own smooth undulating contour data. Of course you have to pick the resolution so that they match and the SRTM data is something like 1 pixel per km which is pretty coarse. You can butt many SRTM DEMs together to get it even more coarse but getting finer data is a challenge. There are other data sources than NASAs SRTM but it can be hard to get the right area of earth and NASA data is public domain and usable. I like to grab the Himalayas around Pakistan area for some nice peaky mountains. The other climates / terrains are a bit more numerous and less of an issue.

Otherwise your left with adding random noise like Perlin noise to the terrain. You can do that and then put it into Wilbur and it will make it better through the use of its algorithms which take into account the erosion but that takes some skill to work the app. Waldronate on here is best placed to answer any tricky questions about that app. But we have a large number of people who use it and have posted about it with lots of his answers to guide you. Otherwise for a larger monetary costs there are World Machine or Terragen and so on which do similar erosion / terrain modelling. In my opinion tho, nobodys - including my own app for this - does terrain modelling well enough to look as good as real earth data. Its a very hard problem to solve. Probably possible with enough compute power but that has been beyond most people until quite recently. Perhaps someone will step up again with the newer powerful graphics cards processing to do a better one now. AI could certainly be trained to generate the terrain trained on real earth DEM data which would also be very cool. I have not seen that done yet although a Microsoft researcher whos name is just beyond my memory did make a plug in for World Machine that did something very much like that and it was most impressive.