Here's a fun little thing I do with SDCafiine. For every N64 game and inject on my home screen, I removed the dark filter by default, this holds true both in SDCafiine and outside of it. But I also wanted to give the option to play every game in stretched 16:9 widescreen, yet I also wanted to keep the native 4:3 aspect ratio as an option as well. So if you launch any N64 game normally, it will be in 4:3, yet if you launch any N64 game after launching SDCafiine, I've altered them all to then play in stretched 16:9 aspect ratio.
The only exception I have is that DK64 launches in 16:9 without launching SDCafiine, because it's the only N64 game that officially offered a widescreen option as far as I'm aware, so the display isn't stretched in that game.
Only drawback I've noticed is that if you exit any of these N64 games/injects after having launched SDCafiine, the Wii U will freeze before returning to the home screen. Not the biggest of deals, but it does mean you have to fully turn the Wii U off and on after playing an N64 game in stretched widescreen on my Wii U.