Zip file is enclosed. To install the files, on the Mac go to the Applications folder and ctrl-click on the Cura application and select "Show Package Contents". Navigate to the resources folder. The felixtec4.def.json and felixtec4_palette.def.json files go in the definitions folder, the son files with numbers before .def (e.g. felixtec4_palette1.def.json) go in the extruders folder, the STL goes in the meshes folder, and the .35 and .50 files go in the variants folder.
On Windows the equivalent folders can be found under C:Program Files
When you restart Cura after placing these files, you should see the two printer options available in the "Other" section.
Why Cura? I also have Simplify3D, and find that Cura does better with fine detail and has some options that Simplify3D lacks. Simplify3D, on the other hand, still has layer-based profile switching, custom supports, and a few features that Cura lacks. Which I use depends on the circumstances.