Thanks, those are good suggestions. The thing is I have barely any experience with the techier side of cameras and don't really know where to begin with that. I did suspect the provided app was rather vanilla.
Stay with the Moto stock camera app, it's fully functional and there's no need to make things more complicated for yourself using a more feature-rich, expanded function third-party camera app at this point. Teach yourself the basics by getting comfortable with using the app, then later you can look into a different camera app if you need to. Some people just don't, whatever camera app comes with their phone is perfectly adequate while some people are pretty intense on their smartphone camera usage.
You might want to avoid that iPhone camera ebook for now too, the user interface and menu options it details will just confuse you as there are just too many differences between Android and iPhone apps. If you have used a conventional, film-based DSLR camera before, the basic photography principles still apply to newer digital cameras, they've been the same for hundreds of years. But even up until a couple of decades ago, to use a DSLR required a basic understanding of those basic photography principles so they could be applied to the various, corresponding camera settings. Now, the cameras in our smartphones, or more specifically the camera apps, are becoming quite sophisticated and can do a lot of auto-adjustments on-the-fly so even novice photographers can take pretty decent pictures by just tapping on a button. Knowing all those photography ins and outs isn't as big a priority now that cameras/camera apps are compensating that automatically, but it can help one take better photos, especially when it involves things like low-light scenarios or framing a shot when there's a lot of rapid motion going on in front of you. There are dozens and dozens of basic photography sites online, if you really want to dig into taking really optimal photos, it might help to read up on the fundamentals, try perusing through this site:
https://photographylife.com/photography-basics
But again that might be overkill for your needs. If you're focused on just getting familiar with the Moto Camera app for now, you might want to just start using the app and do lots of lots of experiments and test shots. Be sure to go into the Camera app's Settings and look through all of its options so you get a handle on its capabilities. If the app also has it's own Help menu that will probably the extent of documentation available for that app. The issue being most books on this kind of topic will be out of date by the time they get released to the public (especially actual physical books as their production time is longer than ebooks), and it's a matter of economics. To write and distribute an ebook on something like a Moto camera app has very little to benefit (more likely to be a deficit). Camera modules, and their corresponding software, are a continuously evolving technology so even if there was an ebook for your particular camera app, it would be a pretty specific one. There's not just big differences in Android and iPhone cameras, there are big differences between Pixel and Moto phones. (i.e. the Pixel camera module has some specific and proprietary features that only the Google Camera app has full interactions with, so third-party camera apps will work on a Pixel phone but with limitations to those proprietary features.) Anyway, take to the time just play around with your Moto Camera app. Back in the days when cameras required film, it was a matter of paying a lot more attention to your photos but with digital cameras you can just picture after picture and just delete the ones you don't want to keep. Make changes to resolution, toggle between auto-flash and manual-only flash, and any other optional settings. Just take a lot of photos, observe the differences in the resulting photos, and once you're used to using that default camera app, you might come to the conclusion it's all you need, or it will be time to install a more advanced camera app.