For example, if I happened to build something like this: Would it count as emulation or using the console, since it still uses the same stuff? It would use the board of an actual wii though, as I wouldn't use a kit and instead would use my own stuff.

Speaking as someone who doesn't own any consoles, I feel like there's a problem of "How do you verify that it is made from the correct parts?"

Yeah I can imagine that that would be the biggest issue. Even if it uses stock parts, I would wager that most communities would consider it emulation or some other form of unofficial hardware. I guess technically it would vary community by community but I wouldn’t be surprised if a lot of places classified it as emu or just straight up didn’t allow it.