We are a wallet, so there are 2 scenarios user can do:
User creates a new wallet: in this scenario, we want to detect if the user (by using Google Auth) is new in web3Auth Network to navigate to create a wallet flow
User imports a wallet : we detect that user already has account in web3Auth so navigate to import wallet flow
How can we detect between a totally new user and an existing one when using Plug and Play SDK (Mobile SDK)
Using the getUserInfo function you can get the details of the user when onboarded, you can check in your database if that user exists or not and accordingly mark them. Additionally you can use our server side verification feature (https://web3auth.io/docs/pnp/features/server-side-verification) for checking if the user if old or new using their wallet address.