Switch (docked mode) – 1080p / 30 frames per second target
Switch (handheld mode) – 720p / 30 frames per second target
As for MGS1:
“arrives virtually unchanged, as this is an emulated version of the 1998 game, lacking widescreen display or up-ressing, which may come as a disappointment for players hoping to play MGS1 on their 4K TVs”.
Just saying, 1080p doesn’t necessarily indicate whether it’s wide-screen or not. 1080p refers to the vertical resolution - the horizontal resolution of the title could be the full 1920px or it could be a 4:3 image bordered by black bars. Still 1080p.