Don't know about OoT but Majora's Mask on VC has numerous improvements: widescreen, textures and framerate (still pretty choppy though).
Majora's Mask (and VC OoT) is not widescreen. The game outputs a 4:3 image, which the Wii (and Wii U in Wii mode) annoyingly stretches to fill a 16:9 screen, making all of the characters look deformed compared to the original. This can be fixed on some TVs by setting it to 4:3 mode.
The textures also have not changed. Framerate improvements (as in a reduction of framerate drops, not an increase in the maximum framerate), if any, have nothing to do with any changes made to the game itself, only the more powerful hardware it's running on.
What has changed (IIRC) is that the game, like other N64 VC games, is running at a higher resolution than on the original N64, which will appear to make the image look sharper, especially if you're using component or HDMI. But the textures are as blurry and muddy as ever. MM had better textures than OoT to begin with because of the use of the Expansion Pak, which is included as part of the emulation.