the logic evades me == need education

[Initiostar]

Here is a guide to the popular mobile resolutions in 2019: https://deviceatlas.com/blog/most-us...en-resolutions. There are many other reports, but this is a good guide.

I use 480px and 1200px; maybe consider Export Options/ Scale-to Fit-Width with the Maximum Width same as page width. I have tested these resolutions on various mobiles including the compacts.

[Acorn]

Change the suggestion to something that works for you.
I doubt anyone would use 480px anyhow.

If you expect the SmartPhone to be used in Landscape then design a bigger Variant that is smartphone-friendly in a larger width to your Main or repurpose your Main to be the simpler smartphone presentation.

Acorn