You can spawn a layout generator with the height equal to the maximum height permitted in the project, see the general setup in the project settings.
Otherwise there’s no right or wrong way, it depends so much from the extents of your world. If you recreate a large portion of terrain then you’re going to have very different altitudes, from the Everest to low hills, it’s obvious that the mountains will make everything else irrelevant. I have seen that in these case it’s better to ignore the heightmap for those lower features and just have the textures, alternatively if you want heightmap for all of your terrain portions it’s better to completely renounce to achieve a realistic scale.