A breakthrough for me as a musician, and particularly as a composer, was when I stopped imagining harmony in rigid frameworks. The first instrument I excelled at to some degree was the guitar (being a fairly average pianist), and that had a great impact on the way I thought about chords.
When I was younger and first getting into learning about harmony I was always fascinated in particular by certain jazz pianists and their ability to string long complex chord sequences together, drifting in and out of original key with ease.
The CAGED system is a method for quickly and logically learning all the potential chord inversions for the guitar’s fretboard. Ordinarily the basic shapes are taught to you and for playing in bands or basic accompaniment, this is fine.