Just back from the 2019 World Cruise.
The visa requirements are listed in the Cruise Personalizer. Find your booking, then in the left column under "Booking Details" select "Visa Travel Requirements". Be advised, that countries do sometimes change the rules, so be sure to re-visit the details several times as the months pass and your embarkation date nears.
Money. As mentioned above credit cards are very, very widely accepted. However, remember that if your credit card issuer suspects fraud they will either suspend service until you contact the institution or worse still issue a new card with a new account number. Problem here is you have no way to get the new plastic from the financial institution. Our solution was to take 3 or 4 different bank cards so we knew we would always have a working card. I would also suggest you dedicate one credit card to your Princess Folio and not use that card for any other purpose. Princess will charge you credit cards several times during the cruise.
The card we typically used ashore offered a feature that sent an instant email for every transaction. Often, while having lunch ashore, I'd get the email before the restaurant returned my plastic to the table. This is a great feature, and allows you to confirm that not fraud is taking place in almost real time. The email provided both the foreign amount and the USD amount. Ask your credit card issuer how or used they web site.
Physical Cash. Do not rely on ship's Customer Service Desk having foreign currency for every country. While they may have some cash for larger countries (Australia, New Zealand, etc.) they may not have a large stock(or any) for less frequently visited countries. Everyone will say use an ATM upon arrival, and this is the best advise. We did order in advance some foreign currency from Travelex for countries with multiple port calls. Yes...Travelex is a bit expensive, but it is so easy to order via their web site and it is delivered via FedEx.
Finally, we did not do this but many WC passengers did.....order a pre-paid debit card. You can use the card anywhere a credit card is accepted and it is totally separate from your own identity and other cards. You can add move cash to the pre-paid card via the issuers web site.