If I pay with a credit card to file my taxes will \I still owe a processing fee?

The $40 refund processing fee is ONLY used when you select to have the TurboTax account fees paid from the federal tax refund.

There is not a fee to e-file your tax return.

Did you choose to pay for using TurboTax by having the fee taken out of your federal refund?  That means you will pay an EXTRA FEE of $40 ($45 in CA) to have a third party bank receive your refund from the IRS, take out enough to pay TT, and then send you the rest of the refund.  ( The third party bank keeps the $40 or $45 fee for itself.)

You do not have to do that.   Pay upfront BEFORE you file --- pay using a credit or debit card.

REMOVE REFUND PROCESSING FEE

https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-account-billing/remove-pay-refund-fees-turbotax-online-change/L7UxC6ZZp_US_en_US?uid=m6r4xelq