Thanks for both your replies. What i am trying to get at is this.
https://imgur.com/a/BlfM8
Nintendo switch use 1280 x 720 to 1920x1080 pixels on the TV and 1280 x 720 on the hand unit.
Switch Screen to the TV it stays in HD artwork
Depends on the size of the TV. Ex if you got a 32" it will look ok when you sit a 1.5 meter away and see it as HD. But if you got a 75" it will look bad if you sit a 1.5 meter away. Because you will see the pixels and experience bad quality and don't experience it as HD.
But if you sit 3.3 meter from the 100" TV the image will be just as fine as the 32" and be in HD. This is because you view the 75" screen as large as the 32" in your eye view.
You can try this at home. Take a low resolution image on your phone. Ex 800x600. And send it to your PC (hopefully you got a 21" screen at home else you need a 640x480 picture). Display it in full screen on the PC (picture will look really bad) and at the same time on your phone (picture may look somewhat bad). Now hold your phone in one arm and look at the phone and the PC screen at the same time and move your phone back or forth so you see the image as nice as possible like you experience "HD" (so no pixels) on the picture on your phone. Now while holding your phone in the same distance to your eyes. Move yourself back or forth until the PC screen is as large as your phone screen (phone screen and PC screen take up the same degrees of your visual view). Now the PC is also in "HD".
Conclusion. So size of screen, distance to screen, resolution on the screen need to match up. HD is a relative definition.
How do Nintendo do it then. You now understand that Nintendo use a resolution at 1280 x 720. So they draw the cut-scenes in hd art on this at a scale of 1:1 to make it appear hd on certain distances and screensizes. Then they have some pixel art as game play. If you draw pixel art on a 1280 x 720 in a scale of 1:1 they will appear as hd and not as pixelart and be very small. So you need to move the pixelart towards you, scale it up to ex 4:1. Just like you moved closer to the pc screen. You need to disable interpolate between pixels and make it scale using nearest neighbour. Now you have hd and pixelart on the same screen.