Aspect ratio: I think the reason why Mario 64 is not widescreen is that some objects (like doors) only get loaded in whenever more than 50% of their surface is inside the 4:3 screen window. You can check this out by standing in front of the castle, go into "first person" perspective and slowly move the camera so the doors are at the very edge of the screen. I remember playing Mario 64 on an emulator with widescreen and a lot of objects were only visible when they were inside the original field of vision. Guess it would've been a bit of work to change all this so they kept the game in 4:3.
They shouldn't have been lazy and just emulated. Super Mario 64 has a native unofficial port thanks to the source code leak that runs 1080p60fps 16:9 with updated camera controls. If people can do it in their spare time Nintendo should absolutley have done it. Hobbyists created a superior product for free. 720p 4:3 is just a terrible port.