@hollosch rather than dimension, I believe image/writing itself is more important. You can move/adjust the picture after you upload it; however how it looks on the desktop will be different from how it looks on mobile.
Here are the examples from our site:
on mobile:
IMG_5766 copy.png
on desktop:
Screen Shot 2022-01-05 at 2.56.15 PM.png
I guess you can see the difference...
