[Xiaomi Mi A2 Lite Themes, Apps, and Mods] rob.1:
Google Camera (all versions) running Pie OS has been very hit and miss in the focus problem, and therefore until a developer or OTA update can fix this issue, it is not recommended for pictures that matter. It is inconsistent as to when these issues occur. This being the case, if you are plagued with the Pie update, your camera performance results will not always be good.

After extensive testing with many hundreds of comparative photos taken with many camera apps this is the simple final conclusion:

Note that all these (except the stock app) require Camera2 API. Instructions elsewhere on this site.

For outdoor photos in bright light: Winner Stock A2 Lite camera app with the following settings:

Picture Quality:High, Contrast:Low, Saturation:High, Sharpness:High. These settings tend to take faster photos than HDR with similar results.

Note that all the camera apps work about the same in overall picture quality and only minor emphasis on color variations. While the google Cameras had a better saturation and warmer tone, the HDR artifacts in the sky make the photos only usable at lower screen resolutions. That limits your ability to crop or enlarge to bigger sizes. The stock camera did not exhibit these with HDR on.

For Indoor and low light: Winner in every test was the Pixel 2 camera app (GoogleCamera-Pixel2Mod-Arnova8G2-V8.2.apk) with HDR off or on depending on light levels. It produced sharp photos with surprisingly good clarity. The stock app was normally muddy and gcam 6+ was too grainy. As a bonus, the portrait mode zooms in (like the gcam 6+, which makes people look less distorted) and there is a motion video option (not tested yet) and lens blur that works better than the 2 lens system of the stock app, but the photos become only 5mp. Like the GCam 6+, HDR for solid color areas (like sky) had the same pattern. Haven't played with all the developer settings yet.

For ultra low light: Winner is the Google Camera 6 (MGC_6.1.013_MiMAX2_V1b_A8.1+fix_Hexagon_failed+blFront.apk) using the night sight feature found under More > Night. The idiosyncrasies of spontaneous app closure when a second shot is desired is annoying, however the results from their algorithm of image stacking is very well done. It also works well to create the smooth water motion for water falls and cascades, but only in dim light.

The gcam 5 app (GCamera_Mod_v.5.1.23_R5Plus_fix_crash.apk), that interestingly the pixel 2 app is based on, did not win in any category.

So I now have 3 camera apps to choose from depending on the photo required. Download an icon app to distinguish the 3 easily. I would imagine these results would be similar on other phones as well.

A note on HDR. None of the phone camera apps do HDR the way it is intended. In normal photography, HDR lightens areas in shadows and darkens blown out bright areas for a more usable photo by combining under exposed, properly exposed and overexposed images that are stacked and aligned. In all the camera apps tested, it makes little difference to shadows and even made shadows darker in the gcam HDR modes. What it does when needed is take multiple underexposed images (each at a faster exposure or lower ISO) and combine to increase (not decrease) contrast for a more vivid (but often artificial) contrast look, while better saturating colors and less noise for hand held images in low light. To do a proper HDR, you need to bracket the exposure and combine in photo shop (PS). There are phone apps that allow exposure bracketing and create the HDR in PS if you really want to get that involved. HDR+ only uses HDR when needed and HDR+ Enhanced the HDR is always on. When no HDR icon is visible, HDR is the HDR+ on when needed (auto mode).

I am currently running pie, and random focus issues have been surfacing for all the gcams. I read a comment that may be an issue with pie vs oreo, although not certain. It seems like Android One users are Google Beta testers. Pies battery life is much worse and no way to see what apps are causing the drain. I suspect it will get fixed in an update. Not for this forum though, there are already many out there for this issue. Main camera is set to Nexus 6P and Front camera a Nexus 5. I read elsewhere that this was optimal, but did not test if the others made any difference. The Nexus phones DO NOT use the same camera (sensor & Lens) on either the Front or Back camera so I am uncertain how much difference the setting actually makes. Most of the other settings were left as installed, although I am still testing to see if any improve the quality. Please chime in if you find any improvements and I will test and update this post. There is always room for improvements.

I would really welcome a more stable google camera build without the focus, night sight and HDR pattern issues. If someone has a line to the developer of these modded apps, please let them know.