> and are adding to the confusion.
> had gameplay in them... and as far as I know and understand US law and its current interpretation, Nintendo is likely well within its rights to DMCA gameplay.
No, not for informational purposes. Nintendo doesn't have the right to (for example) demand a review video come down just because it doesn't like the coverage -- even if the video includes gameplay. If the emulator tutorials showcased large swaths of gameplay then that would be a problem, but snippets would not fall into that category.
Copyright has limits. Companies often try to create the impression that every review, article, tutorial, or blog post that references their products only exists at their pleasure. But that's not actually how copyright works. You can't take down a news article or tutorial unless it's using those snippets in a way that goes beyond fair use.
Of course, Nintendo technically can take down those videos, but not because there's a legal right to or because they're protecting their IP; Nintendo can take down those videos because it has a bunch of lawyers and can threaten to ruin your life regardless of the eventual outcome of any lawsuit, and because Youtube will take down the videos for Nintendo without ever checking to see if Nintendo is abusing the DMCA/takedown process. But that's a separate conversation.
As always, IANAL, but including a snippet of gameplay from a Nintendo game in a tutorial about a Nintendo emulator is probably perfectly legal.