Creating a new world
For the sake of simplicity, when creating a new Build the Earth world, use the World Type: Planet Earth in the More World Options..., clicking on Customize, and choosing the Build The Earth preset as shown below.
But if you want to manually configure the world options, using the world type Planet Earth, then click on Customize, select the BuildTheEarth option to use it as the base, and then click the Customize option to customize it. You will then be prompted with a customize screen that will already have the Build the Earth options filled in. If you want to play Build the Earth, ensure the options 1, 2, 3 and 4 are configured as shown bellow. The rest, such as the CWG preset, the default dataset settings or the population settings can be changed.
If you are experiencing problems delete terra121.cfg and terraplusplus.cfg from the .minecraft/config folder, delete the terraplusplus folder in .minecraft, and start over.
You can contact me on Discord, under davixdevelop#3914, or you can join us on our BTE Development Hub on Discord, and ask away under the #terraplusplus-support channel.