When your RBF is disabled on both sides of the transaction while sending it, the Childs Pay for Parent (CPFP) transactions can always come in to alter the transaction fee and get it confirmed faster.
There is no such thing as RBF on both sides of transactions. A transaction is RBF-enabled or RBF-disabled.
CPFP can be done only if you have full control over one of the receiving addresses. So, it's not that CPFP can be always done.
Can this CPFP always ensure that you will be able to alter the parent fees to speed up the transaction? If it works on Electrum, do other wallets adhere to the same consensus?
If you have the private key of the one of the receiving addresses, you can use electrum or any other wallet that allow you to spend unconfirmed outputs to do CPFP.