In Electrum wallet, mempool is the best option if we need to choose one default option for transaction fee estimation.
The best is to use your own node mempool like Bitcoin Core to set the fee.
This thread is about Electrum wallet and options to set fee rate for a transaction.
If you read my post and my thread, you will see that I only suggested Mempool as a best option if you want a default one but it is still overpaid and the best of the best (in Electrum wallet) is double-check with mempool site before you pick a fee rate for your transaction.
Running your own full node will give you more accuracy of information about what's going on the network, mempool as well as give you better privacy, I know that.