I just wrote a long post that suddenly disappeared. It wonderfully, and clearly, outlined, using the Nashville numbering system, the linkage between chords in a key and the related modes (each with a funny name). The basic idea is, ignoring approach notes, chromatics, and all of that stuff, that there are seven chords within each key.
Just using roots, fifths and octaves, even the major/minor distinction between chords is lost (although it is implied - that weird seventh chord with it’s flat 5 is an exception). Add thirds, and the major/minor distinction becomes evident. Add sevenths, and more distinctions occur. Finally, add all of the notes of the key into each chord you get the modes. Remember, you are just starting at a different note of the key and then adding notes of that key. If you are playing chords you are at least implying different modes. And, some modes are more important to different types of music than others. In a I, IV, V genre, the Ionian, Lydian, and Mixolydian are the implied modes, although would just say the first, fourth and fifth.
How much of this did I get wrong? I’m shooting for 85%.