They'll use ANY balance in account first (no choice in that, even if it's only partial payment for the item), then, if you are "verified", with bank account linked, pull the rest from bank account.
You can change the option to pull from bank to credit card, assuming you have cc registered there also. It's an option before you complete the transaction. Note, though, that it always defaults to bank account, so you have to choose the cc option each purchase.
If you've already done the transaction, you must have just not seen that option, and it tells you where the funds are being taken from in the smaller print.
Anyway, you do NOT have to move money from bank account to PayPal account. Matter of fact, this takes several days to do so, and your seller is not paid till then, whereas payment to seller from bank account (or credit card) is instant.
- OS