How to know on which Google account text messages (SMS) are saved? I have 2 Google accounts on my phone. How can I know on which Google account text messages (SMS) are saved?

I use a Samsung Galaxy S5 SM-G900A with Android 5.0.
Currently, text messages are not saved to your Google account (however useful that would be...). However, Hangouts are saved to your Google account, and you can check which account is active in the Hangouts app by swiping from the left and checking which profile is shown at the top of the navigation drawer.