RE: Divide and Conquer – Music Theories
>I'm endlessly fascinated with independent lines creating a progression of harmonies.
This is actually the original way of creating harmonies, called counterpoint. Even today, much of the "rules" one studies in music theory courses - e.g., watching out for parallel octaves, perfect fifths, and doubled leading tones, etc. - these prohibitions describe and are derived from that earlier discipline of the Middle Ages and Renaissance style periods. The crystalized concept of a "chord progression," a series of vertical blocks of notes, came along a few centuries later.
That said, a thorough study of counterpoint - in theory and in practice - should be part and parcel of every musician's harmonic/melodic "bag of tricks."
[Edit:] Very good that you are learning about principles of orchestration, the three 'grounds', etc. What textbooks on orchestration have you been examining? Personally, Samuel Adler is a good place to begin. There is also an excellent YouTube channel on orchestration that you might want to follow. Link: https://www.youtube.com/user/OrchestrationOnline