Lots of great advice here. You should never find yourself in a situation where you have the verses and then must decide on a chorus, you should plan ahead. It's about how the whole connects through the bits, so if you want unsettlement in the verses you could let them avoid the root, and release the root in the chorus, and vice versa. For me harmonization is all about interpretation of what the song is about, and working with triggering emotions through tension/resolve etc. Embellished chords are great, but also slash chords with different bass notes in them will do wonders.

Todays A-team in Nashville, with Brent Mason up front, is very knowledgeable about the great guitarists and even jazz/fusion guys like Larry Carlton etc., so the simple stuff is not always that simple anymore. Those guys just makes things seem so simple by world class technique and fantastic rhythm chops!

Also a thing not to be forgotten is the polyphonic approach, where the bass is playing one note of a triad, the singer is doing another, and perhaps the guitarist a third - creating harmony together! Also a great way to avoid the usual suspects of block chording through a song, creating air and great mixes.