proph will it start reporting data from the container back to google servers like location or whatever other data it wants to report?
Yes. If Google is using Play to help you determine your location then they're definitely going to store that. I have google stuff installed on my main profile for push notifications, mostly. I just tried find my device for fun and I got a push notification. Google reported back my phone's battery, but location was off so it couldn't find it. I turned location on and it found my exact location. This is why I keep location off all the time unless I need help with navigation.
The big difference that others are trying to say above is that Google doesn't have special access to the phone. This means they can't just scan all of your photos and send data back to Google. If you don't like them accessing sensors, you can turn that off. In fact, I didn't have the triangle thing on Google Maps telling me which direction I was facing until I turned on access to sensors. On stock, Google has unlimited and administrative access to everything. Hypothetically, they can change any setting or install any app on a whim, even ignore or change settings about blocking camera, microphone, or location access to apps, but not on GOS.
I'm not an Android dev, but I've done a lot of poking around. The reason the app cannot have these kinds of special permissions on GOS as opposed to stock Android is because of how system apps work. System apps are installed with the OS, and on Android certain "dangerous" permissions are restricted to system apps. Since all of these Google Play apps are installed as regular apps, they have no special or "dangerous" permissions. They simply cannot have access. GOS's compatibility layer can have access to these "dangerous" permissions, but they don't (only permissions are location, notifications, and sensor access).
proph If I sandbox g services and Signal to get the push notifications working then what data am I leaking to google with push notifications?
Apparently nothing. The push notification just sends a message to the Signal app on your phone, triggering it to wake up quickly in the background to retrieve your messages. No privileged info is sent to Google.