Yeah, it's actually pretty easy to set it up in VLC so that they play in two windows, but are affected by one set of controls (e.g. pressing pause pauses both at the same time; no ninja skills necessary):
1. Download both videos.
2. Open VLC -> Media (at top) -> Open Multiple Files...
3. Add... -> Select the video you do not want audio from (*cough cough Jeff's*)
4. Tick 'Show more options' -> Tick 'Play another media synchronously' -> Browse...
5. Select the video you do want audio from,* click Play, and enjoy!**
*this order should be correct, but it can be a little finicky and you may need to swap them
**enjoyment perhaps best across two monitors
It super-super helps that both videos are nigh-perfectly in sync. I don't know how to time delay them, my next plan was to cut one with ffmpeg. But we're good!
EDIT: Ok, now that I'm trying to watch it, there is a one-second delay on Jeff's feed. It's not too bad, but if you're so inclined, here is an ffmpeg command to tighten it up:
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