I would ditch earn.com -- it overestimates quite a bit.
BTC.com isn't too bad, but I definitely prefer
Johoe's site for a fuller picture.
I do use Electrum, but since I've been checking the actual fees, I've never had to use RBF.
I always check the mempool before sending, too. It doesn't come up too often, but occasionally I'll send a transaction, then there isn't a block found for 1 hour or more. Average fees rise, transaction gets delayed even longer. In those cases, it's been helpful to have the RBF option.