Pixel perfect is the best way hands down.
I found that setting screen resolution sometimes fails spectacularly resulting in a black screen, so I would avoid that.
Regarding the resolution you should upscale to, you should just make sure that the screen proportions (with and height) are correct. Pretty sure that Unity fits it the screen in fullscreenmode as best as it can.
I follow this guide line: https://blogs.unity3d.com/2019/03/13/2d-pixel-perfect-how-to-set-up-your-unity-p...