The entire palette for song creation is right in front of your eyes. If you really want to supercharge your ability to write and play songs, this book can do the trick. It will also provide plenty of opportunity to develop your ability to flat or finger pick chords, It can provide tasteful combinations of single note and multiple notes for primary and secondary guitar parts. You will never be lost for just the right chord again. You will sharpen your mental abilities without giving yourself a headache.
Scales define keys.
Every note in a scale generates a family of chords. More importantly each note of a scale generates one specific chord. Chord naturally falls within a scale and they are an integral part of a key. This is how chords are created in the first place. If you do not understand this, you will struggle with chords for a very long time.