Hi

I have been reading that pre-booking the Narita express is advised. Otherwise, I might have to wait for several trains later. We will be in a group of 3, each of us with a large suitcase.

But what if I prebook it and then my flight is delayed / I miss the train because it takes a long time to get through immigration / wait a long time to collect luggage / It takes longer than expected to get IC card and sim card (lots of things that can go wrong in my mind!).

If I miss it, will they let me change the time of my reservation or would I just have to buy another?

Also, same question for the bullet train, as we will travel to Osaka, Kyoto and Hiroshima on this trip. If I prebook the bullet train online, it is possible to change it if our plans change? Or if we miss the train?

Thanks