ATM/Cash or Credit cards?

Fees? There are credit cards available that do not charge foreign transaction fees. There are bank accounts, e.g. Schwab and CapOne, that do not charge fees for ATM withdrawals, and Schwab refunds the other bank's fees. In general, bank-owned ATMs in most countries in Europe (Spain and Italy are exceptions that come to mind) do not charge fees for withdrawals - I do not know the situation in Norway.

My Capital One Visa Quicksilver credit card actually has negative fees - no fees with a 1.5% cash back. My ATM does not have a FX fee. That said, I use my credit card most of my Norwegian purchases limit use of cash to small purchases (under 500 NOK. BTW Norwegain ATMs tend to demoninate cash returned with 500 NOK bills.

No problem using my chip and signature credit card in Noway. This included using the chip and signature for train ticket vending machines - no PIN needed.

Edgar--correct! I don 't even think about the cash-back aspect anymore, other than which card has a quarterly bonus for what category. One could state that for some time now you may as well use a card for everything you purchase because the merchants' fees have any now become a permanent part of the price.

https://www.numismaticnews.net/world-coins/norway-moves-cashless

Norges Bank, the central bank of Norway, recently reported it
calculated Norwegians are using coins and bank notes for about three
to four percent of their financial transactions. This makes Norway the
most cashless society in the world, ahead of neighboring Sweden.

During our last 2019 trip to Norway I discoverd that some of our old NOK notes expired and we had to take them to the Norges national bank to exchange them for new notes.
https://www.norges-bank.no/en/topics/notes-and-coins/Regulations-withdrawn-notes-and-coins/

How to recognize valid bank notes:
https://www.norges-bank.no/en/topics/notes-and-coins/New-banknote-series/

To be honest, I would be surprised if shops in Norway even wanted to handle cash. They pretty much use card only. You might ask your card issuer if they can upgrade your card to "touch to pay" if you already do not have it. That would make most transactions easier.