I used one Google account to set up Google WIFI in the Google Wifi account more than a year ago and a different Google Account to set up everything else in Google Home. I have migrated the Google WIFI to Google Home but it is under a different Google Account than the rest of my Google Home devices. I want to migrate the Google WIFI points to the same Google account as all my other devices. It appears I may have to reset the Google WIFI points which would be horrendous given all my ring devices would need to be reset.
It might have been possible to invite the old Google account to the same Google Home as the one created by the new Google account. However, I'm not sure that's possible now that it sounds like you've already migrated it to a Google Home under the old account. So, you may need to factory reset them to get them into the new Google Home under the new account. However! That does not mean you need to reconfigure any of your existing WiFi clients! You just need to make sure you set the system up again with exactly the same network name (SSID) and shared password. If you do that, all of your existing WiFi devices should reconnect automatically.