How do I find the right screen resolution and camera zoom

I want to develop a mobile game with 16 x 16 sprites. I would like to support resolutions from 640 x 360 upwards. I want to show on screen 320 x 180 and move the camera accordingly.

Would I set the game resolution to 640 x 360 and zoom in with a camera?
Would I set the game resolution to 320 x 120 because that’s the screen view?
What happend if devices have full hd resolutions?

Thanks