In App Purchase workflows per device?

I’m working on my first RN app and I was looking to implement In-App Purchases for subscription revenue from my members. For my RN package, I’m using react-native-iap which has a single call for getSubscriptions or requestPurchase yet it goes to both ios and android stores and returns their results, which vary. I also have a node server setup to receive notifications from both platforms, but after connecting googles server notifications, it seems they do not return any custom data associated with my user. Meaning I have to revise my workflow for google to save the transaction token on the initial purchase from the app, which I did not have to do with apple.

Before I venture even further down this path, can someone confirm this workflow? The react-native-iap sample is pretty bare bones but it handles both ios and android. When I go to implement this in a production app, i need to carve out clear paths for ios and android? I need to take google subscription response from the app and send it to my api before i can start to get server notifications from google? In contrast, apple lets me send an account id up with my subscription transaction and they then send that id with every server notification. Google only gives me a transaction token, which i need to save, and then use that to match to my customer?