So you've never heard "Birth of the Cool"? Was Gil Evans first collaboration with Miles (some of the latter's first recordings as a leader) but it's just a nonet so the arrangements aren't as overblown as the later stuff. The songs are also tight and short, a carry over from the bebop era. Definitely worth a listen.
Yeah "Our Thing" is good but not one of his best- the debut does everything it does but better. Besides the debut, the prime Henderson slabs IMO are "Power To The People", "In Japan" and "Inner Urge".
Kirk definitely had his commercial side. He's such a talented musician he's usually able to keep things interesting even when he goes that route but it still feels a bit watered down. Btw since you're getting into Quincy you might already be aware of this but the 2 collaborated a few times, resulting in Kirk playing flute on this, which you'll recognize as the theme from "Austin Powers":
If you're into Sonny Clark, this is the best stuff I've heard from him (early recordings from Green, ore in the soul jazz vein than his later stuff but really ####in cool, maybe the best soul jazz I've ever heard): https://www.youtube.com/playlist?list=PLea9tj3kSsQZtVj0-CkwSc5__ymviBDTC