https://cloud.google.com/bigquery/docs/enable-transfer-service
Install ODBC driver x64 on your local machine. If you're going to have Server run your BigQuery workflows for you, you'll need to also install it on your Alteryx Servers.
You'll use your google account to Sign in and to check out a refresh token to authenticate your ODBC requests. A word of caution: I don't know what happens when your account's password expires... Should be interesting to find out. I also don't know how well this will work from the Server and what alternatives exist for a system account besides personal logins.