Preview photos and photo results are different when using the lightroom camera.

Hello @Irul 

You are correct, there can be differences in appearance between the capture preview and the resulting DNG image that LR Camera saves.  The preview image image shown is a JPG thumbnail that the OS APIs deliver to our camera.  JPG images are processed, but DNGs are not.  Upon saving DNG images from the LR camera to one's LR library, a basic camera profile is applied (Adobe Default), which you can see & change in the app Settings under Import.  Adobe Default and even Camera Settings used as Raw default settings will apply profiles to help DNGs look better than completely unprocessed raw images.  However, these simply will look different than the heavily processed JPGs displayed as preview images.

I find myself using HDR Mode even in situations without a lot of contrast, as I usually like the results. (I also always save the "original" image which is an in-camera setting.).

I've noticed on newer, larger camera sensors in the last few generations of iPhone, the DNGs can often appear overexposed relative to what the camera viewfinder depicted.  This is again a platform issue, where the video that iOS provides the camera viewfinder is designed to have different display characteristics vs the full raw data that DNG captures get.  In Pro and Auto mode, I often drag my finger left across the camera screen to use Exposure Compensation to decrease exposure a notch or two.