We had a wee discussion of them over here 
https://forum.fairphone.com/t/pixel-camera-app-google-camera-port/53146
Personally, I find OpenCamera really good, especially if you get HDR on and are able to hold it steady for a moment.
I’ve tried the Pocophone GCam port and it works well. All produce quite different images from the same scene which is quite weird, I guess the processing is quite different on all the apps.