Hey Luke,

To be honest i think it depends what you want to do with it.

I also think that Ued 1, Ued 2, Ued2.1, Ued2.2 are actually suitably equipped well enough to create proper terrain/organic geometry with. It would be better to use a free tool like 'Blender' or another 3d modelling tool to create terrain geometry with.

https://www.blender.org

There are some plugins for Blender that are useful for this, like the .ase scene exporter plugin, which after exporting the .ase files, you are able to convert them to .t3d.

However, I'm not sure some of these useful plugins are compatible with version 2.8, but they are compatible with Blender version 2.79.

If you choose to go down this route, I'll try to offer you some help with Blender, since before making world geometry for an UEngine game in Blender, there are some things that you need to set up correctly first.

I hope my post was helpful!