Well I bit the bullet and went with my wife to exchange her Note 7 at the corporate store. To their credit, they have usually treated us well, and they all were at least on the same page about allowing a double exchange for any phone in stock, including the S7 Edge. That was about the only up side...
I wasn't watching the actual exchange process, but was watching the kids while my wife went through it. All I know is they told her it was activated and ready to go. We went to run another errand and later noticed the S7 Edge wasn't activated and was stuck. By this time the store was closed, so going back wasn't an option. Long story short, I was escalated to Tier 2 support on the phone, where they determined the new SIM card they gave her had a cancelled status. Basically the equivalent of having a black listed IMEI from what I can gather, and she couldn't override it. So one of us gets to go back to the store tomorrow for a new SIM card.
I tried to swap it with the SIM in my Droid Mini backup because they're the same size, but even that's a no go because her line is currently in limbo. Going into our account, it currently shows no device is active on her line to change around.
So after all that work trying to figure out how the exchanges would be handled, I'm blindsided by something else unrelated. And I still have no written confirmation that the double exchange will be valid when the new Notes come in. DX