And you can completely trust the entropy of electrum seeds or BiP39 cause it's not practically possible for anyone to brute force in million years.
If your seed phrase has been generated by electrum, you can be sure that it provides enough entropy, but if your seed phrase is BIP39, it depends on what software you used for generating your entropy. For example, if you generate your BIP39 seed phrase using a close-source wallet, there is no way to know how it has been generated.