…within reason. I know that the top answer will be to flash a different OS on your device. A lot of us are not at that point right now.
So I was texting with my wife in Spanish and suddenly a system bubble popped up, “would you like to translate this to English?” At a minimum, this means that Google is reading the words on my screen at all times to detect the language. I don’t know if this is possibly done on device, but translation certainly isn’t. I’ve already changed my system translation app to Translate You.
I’ve noticed other times that Google watches or listens in the background. It has a feature to detect ambient songs playing, for example.
What other standard settings should I check for to prevent Google from watching and listening to my phone in the background?
Anything that runs the Android version that came with it will gather data on you and short of permanently disabling the data connection, you will not be able to escape it. Google gives back door access to everything it wants, constantly sends encrypted data packets to its servers that only they know what they contain and doesn’t give you the ability to stop any of it.
If you have a Pixel phone installing GrapheneOS is incredibly easy. It gives you full control over what the apps installed on it are allowed to do on your phone, including Google’s if you wish to install them (unlike on other phones where the privacy options are grayed out for them and permanently enabled). Mind you, you will lose some functionality if you block everything. But you are empowered to decide which apps you trust to do what on your own phone and disable what you don’t need.
If you have something else than a Pixel, LineageOS is an option, however the installation process might be more complicated.
Mind you, with the FOSS alternatives you will sometimes experience some jank or advanced features that don’t work. But it is a tiny price to pay to know you’re not giving your data away. It has gotten far better in the last few years as well, at least from my experience with GrapheneOS