I’m not really the one to ask as I don’t buy a smart phone for a camera. However, it looks good to me and I have a picky eye. And from what I’ve seen, you can use Google Camera on Grapheneos and get the same quality pictures and video.

I was very disappointed with the (default) Camera after switching to Graphene, luckily you can just download the Pixel Camera (including all the Pixel optimizations) from Play Store on Graphene OS or download it as an APK bundle from some other sites (downloading the normal APK won’t work, it has to be the bundle).