So my friend told me it isn't that secure if you have access to the source code of the Obfuscator, so I think it would be better if you would use that obfuscator and Auto Py To Exe, so something like that:
plusobf.py Script.py '+=+'
And then use Auto Py To Exe (You can start it with the command: python -m auto_py_to_exe)
That should be secure enough.
But where you can see the source code of the obfuscator? at least not on github, the code is also obfuscated there