IPHONE 12 PRO MAX PHOTOS GRAINY even when taken in bright sunlight. camera settings to blame?

When trying to take photos of cotton woven blankets held up in the bright sun, with the sun behind me & hitting the blankets strongly, two things happen a lot:

1 - either the photos come out grainy and darker than to the naked eye

2 - if photographing a light colored blanket (say cream) from 3, 5, or 10 feet away, the cream blanket will sometimes have yellow squiggles in places. Almost as if the iphone can't handle the brightness?

The ambient temps are not high (70's) and lenses are clean.

Is there a camera setting that could be affecting this?

Could the camera adjusting the photos ISO or something else to try & make them darker because the true light is bright?

3 - How on a mac can I see what format i used to take the photo - ie, portrait or photo? HDR or not? So I can start narrowing down which settings produce better photos?

4 - I just updated to IOS 15.5 which has 'enhanced' info about photos. How do I turn that off or make that info private for posting online?

TIA👍