Foreign currency account is required to pay out currency purchased in Pluskantor.pl. The number of foreign currency account (in EUR, USD, CHF, GBP, RUB) can be added any time in Pluskantor.pl. It is worth to have a foreign currency account in the same bank as the account in PLN to make it easier to make the payments to your account or pay in Pluskantor.pl.
It is best to have an account in PLN and foreign currency in the banks with which Pluskantor.pl is integrated. Banks integrated with Pluskantor.pl include BZ WBK (including former Credit Bank), Pekao SA, PKO BP (including former Nordea Bank), the current mBank (in a group of former BRE Bank and Multi Bank) *, Alior Bank (the the former BPH) and Raiffeisen Polbank.
Within the above banks integrated with the platform currency transfer lasts up to 30 minutes and is free. The exception is mBank (in a group of former BRE Bank and Bank Multi)
For fees, please refer to the question. How much does Pluskantor.pl cost?