I'm beginning to think this is less of a hardware/driver-level issue, and more OS/software related...
I came across a few recommendations for a program called DisplayFusion after looking through some threads in the Nvidia Surround forums and decided to give it a try. Essentially, the idea is to leave the graphics driver in Surround mode and have the software divide up the single display into user-defined segments. This should work fine, since I can run all 3 monitors completely stutter-free while running in Surround mode.
I got it set up and working on a basic level, but came to a screeching halt shortly thereafter when I started noticing frame hiccups while DisplayFusion was running, despite the driver running in Surround mode.
It was extremely easy to verify that the new software was the culprit in this case - I pulled up vsynctester.com in Chrome and verified the hiccups were occurring, then I simply right-clicked and exited DisplayFusion via the system tray icon, at which point the test immediately went back to running stable with no spikes. I didn't need to reload the browser or the page or anything.
This leads me to consider the possibility that there is some inherent issue with the way Windows (10 Professional x64) manages multiple desktop "spaces". Or maybe DisplayFusion just happens to have some overhead that is producing a very similar yet entirely different issue... It seems unlikely.
I think I'm going to spin up a temporary drive with Windows 7 to see if that makes any difference.
I decided to do some further testing with DisplayFusion since the result just wasn't making sense to me. It turns out, the only reason it was stuttering was because I was in the Monitor Configuration dialog in the program. I assume the stutter was occurring because it is polling hardware
during that time!
So, my issue is essentially resolved... It's a 3rd party software fix, but it works nevertheless.
Nvidia Surround + DisplayFusion = win
Check it out - glorious!