Also, the offline Electrum USB cold wallet shows no balance, so in terms of a $5 wrench attack, a new watch-only wallet would need to be created using the offline MPK (master public key) and then entering the passphrase.
Is there a way an Electrum watch-only wallet can have a fake wallet to show a fake amount if under duress? I know hardware wallets can do this.
An equivalent (but a cheaper one) to this decoy wallet scheme would be to create a decoy wallet with one seed and to create the real one with same seed and custom words to extend the seed with the named feature. Then you will get 2 different master public key allowing you to create 2 watch-only wallets. Under duress you will show the decoy one ofc. It works better, if you've written your seed somewhere without the custom words.