Will I be charged extra fees if I use my credit card for Apple payments

No extra fees for using Apple Pay for person to person transfers. Are you referring to Apple Cash? Some instant transfers may have a 1.5% fee.

>> When you transfer money from your Apple Cash card, you can either use a bank transfer to send funds to your bank account in 1 to 3 days or you can use Instant Transfer to send funds instantly to an eligible Mastercard or Visa debit card. <<

Set up Apple Cash - Apple Support

Transfer money in Apple Cash to your bank account or debit card - Apple Support