You can enable your phone to offload originals to iCloud, and only download full-res on demand.

yes that's true about 40% more! You can also leave as HEIC but do:

Settings → Apps -> Photos → Transfer to Mac or PC → Automatic (convert to jpg)

or

In "Shortcuts" app - select photo, convert to jpeg, save file:

https://i.imgur.com/yyUgMm1.png

Set this to just kick in when you transfer/export/share. It generally does the right thing. That doesn't store/keep the dupe, just delivers JPEG to target.