On paper Nintendo is also against people modding their games and put videos about it on Youtube, but they only strike mods that is about what they may plan to do for their next games like BOTW multiplayer mod, playable Zelda mod, any large-scale mod that is like a game of its own, et cetera. As long as you don't put a video that you show yourself entering the game via an emulator you are fine. Those who also talk about how to use an emulator to play a Nintendo game better at risk too yet Nintendo didn't do anything to most of the Youtubers. They are selective on what video and Youtuber actually cause damage. They would be extra sensitive about Youtube channels encouraging pirating Nintendo content and make money from it by having really a popular reach though.
However Nintendo only allows positive reviews of their games in the context of a let's play video which you may read here:
Nintendo Game Content Guidelines for Online Video & Image Sharing Platforms
www.nintendo.co.jp
So Nintendo is pleased you advertize their game for them but they want you to talk about the game in the video, they do not allow simply silent "walkthrough videos". And I publish my videos about how I ruin Nintendo games on me Youtube channel lolol: