KDE Dolphin has a preview option (and you can resize too)..
I think both Dolphin and Nautilus have a preview.
The problem is - the web browsers don’t call the stock system file browser for uploading.
The only combo that worked the way I wanted was KDE+CHROME - which calls “KDialog” when picking files for upload.
Xfce, MATE, Cinnamon - no go! I think I made a post on the Mint forum pointing out this deficiency.
A nuanced thing - but - these are the kind of obstacles you encounter in Linux once you start trying to actually do something.