email login should be used only in cases when you do not have/ want a LN auth or nostr login. Let's say is the backup of the backup login, the last stand in case of SHTF.
But IMHO using nostr as main login and LN-auth as backup is more than enough. Yes, you can login with both, for example you are not at your usual desk, with a proper browser extension using your nostr login, then you can use a dedicated mobile app to use LN-auth. I will suggest to use a dedicated LN wallet app for this. People are changing frequently mobile apps or refresh install it and with that will lose the access with LN-auth.
email login should be used only in cases when you do not have/ want a LN auth or nostr login. Let's say is the backup of the backup login, the last stand in case of SHTF.
But IMHO using nostr as main login and LN-auth as backup is more than enough.
Yes, you can login with both, for example you are not at your usual desk, with a proper browser extension using your nostr login, then you can use a dedicated mobile app to use LN-auth. I will suggest to use a dedicated LN wallet app for this. People are changing frequently mobile apps or refresh install it and with that will lose the access with LN-auth.