Hi, fair enough. I've thoroughly immersed myself in this stuff enough that I sometimes don't realise people aren't as familiar with the concepts and jargon. I'm going to write another article that I think should help about the Klein gordon equation, at some point.
See my last article here https://forwardscattering.org/page/Intuitive%20Quantum%20Ele... Although it is a bit technical. next one will start simpler.