Wow guys, thanks for all the hints.
I went out during my lunch break, and made sure that pressing on/stressing the seatpost and stem, and BB all didnt re-create the noise. I tightened the crank bolts and ensured the pedal clips were snug.
I took the rear wheel off, and was surprised that the wheel was noisy by itself. Which is odd because cranking it on the stand didnt make the noises (at least I thought).
I put the wheel on a truing stand, spun it, and it just sounded horrible.
So took the cassette off. Back on the truing stand. Still horrible.
So began unscrewing the axel - this is further than I ever had been before. Got a glimpse of the ball bearings in there. So then tightened that whole thing up (with a wrench on both sides).
Back on the truing stand and its quiet.
As a bonus, when I put the wheel back on the bike, any lateral movement of the wheel that I had (when pressing the rim) is now gone.
Put the wheel back on the bike and rode it in the driveway. Seemed good. Just took it out for a 30 mile ride after work, started mostly quiet, but seems there might be a few gremlins left. Dont get me wrong, this certainly helped. I think now I can say the remaining creaks have a rhythm of some sort, maybe between 5 and 7 o'clock on the crank, occasionally.
Though I'm a bit concerned at what I've done. If I "freewheel" my rear wheel now, it now does not rotate terribly long. It used to go for maybe a minute after a light push while on the stand. Now the wheel comes to a halt pretty quick. Did I just overtighten the axel! ??? Is it even called an axel? (I presume thats actually the hub).
Ugh, the more I do, the more I am concerned I might be effing something up. I'm gonna check out those GCN video posts (thanks Patrick). And thanks to all for guidance, I've got a laundry list of things to keep checking.