You will get charged the current exchange rate, plus a small sum for converting overseas currency. Example: Goods cost R 245,00, currency exchange was R 8,50 (Nedbank)
You'll need an FNB account if you want to withdraw cash. You can create the account with your ABSA credit card and add an FNB account later if/when you want to withdraw cash. This is exactly what I did.
My paypal account funds is in US dollars. Not sure if it is possible to change that. When I withdraw, FNB converts the amount to Rands at the prevailing exchange rate.
The costs are 3% for paypal to paypal transactions and 1.5% to withdraw to an FNB account.