You will want some kind of text editor or IDE to develop Encompass projects.
VSCode has worked pretty well for me across Windows, OSX, and Linux. A C# extension is available which has excellent C# integration and the editor has various convenient features, like an integrated Git interface and terminal. (Make sure you set the terminal to Git Bash if you are on Windows - this is under File -> Settings.)
Of course, if you prefer some other editor, that will be perfectly fine. Visual Studio is a popular choice for Windows that features good performance measuring tools, and many people sing the praises of JetBrains Rider. And there’s always Vim or Emacs.