My mother was very claustrophobic on our first cruise. I was so concerned we upgraded from an inside cabin to outside cabins. The windows are huge, at least above deck 2. She was O.K. in these. When she got panicky at all she went up and sat on deck 9 or 10. No clustrophobia there, just miles of ocean. Her panicky feelings were gone by about the third day.
On the second cruise we had a verandah, but she had an inside cabin across the hall. She was O.K. with that, much easier for her to cruise the second time, knowing the lay of the ship. She would come over and sit on our verandah when tired and we were off doing whatever.
If you do not want the expense of a verandah, look at the floor plan of the ship and choose a cabin one floor away from deck four, near the aft or forward stairs, then just walk down the stairs and sit on deck 4, lots of comfy chairs.
Few of the other ship locations set my mom off. The restaurants and common areas are all very large. A few of the bars seemed confining, large rooms but fairly low ceilings. But once you get used to the ship, you should be fine.
And, depending on the itinerary you CAN get off a lot.
Carla