For me, "nwjs-ffmpeg-prebuilt" did not make difference. Even without it the original linked Tweeter video played fine on Opera 60 with some updates. I'm not sure what caused this - maybe Twitter re-encoded it at some point with a different codec. I've noticed low quality, and not sure it was the same when I've started the thread. I've tried monitoring the Opera process and did not notice it even tries to access the new .dll file. Someone will have to link a specific video which did not work without this .dll and worked with it.
And yes, https://twitter.com/NOAASatellites is the latest example of how videos don't work under Windows 8.1 even with latest Chrome browser.