I like how 5ths or the power chord doesn't establish a set minor or major. It really gives you the power (hence power chord) to do anything at any given time.

I used to think they were always used soley because the fingering was easy but learning why was wonderful. It has made me try many things. For instance trying to write a song without any fifths, or with only fifths/octaves.

A different chord, scale and arpeggio system for guitarists is Fretboard Logic by Bill Edwards
Its basis is that music theory as generally taught for guitar comes from the keyboard.
This doesn't allow for the guitars weird tuning and fretboard layout. Well worth a read