Yes, they are all the same.
This is an equivalent for PBKDF2 iterations ?
No. Encryption is not the same as just increasing the number of iterations.
The real question is "What are you trying to achieve?" If you want a set up which means your coins will not be immediately stolen if your seed phrase is compromised, then you should use a passphrase, since this is a BIP standard and reproducible across multiple wallets. Changing the iteration number is both less secure than a complex passphrase and non-standard and could cause you problems in the future when trying to recover your wallets.