My sister flew Norwegian and had a bad experience with the agents in JFK. They thought her carry on bag was too heavy, so she rearranged some things, then they reweighed it, along with her purse (personal item) and tried to charge her extra. Then they sent her to the back of the line! There was a TSA person there who tried to get her to go through without going to the back because of the flight time, to no avail. She nearly missed her flight.
The experience on the other end (Stockholm) wasn’t bad. And the flight was low budget, but she was expecting that.