OK, finally figured out how to export the pix in their saved format (JPG or HEIC). Settings>Photos>Transfer to Mac or PC - check keep originals. This scene isn't a great example - not a lot of fine detail - but here's a comparison of one pic shot in HEIC, and one in JPG. Opened both in PS, cropped to a little under 1,000 pixels on a side, and saved as the highest jpeg quality.
First is HEIC:
Second is the jpeg:
The jpeg out of the phone was 4.6 MB, and the HEIC was 3 MB.
And, just to confirm what DG wrote, uploading the HEIC file to the forum didn't work. It shows a page with the corner turned down where the image thumbnail should be under files, when in edit reply.