Rail pass pays for itself if you plan to visit multiple cities. When I went took a day trip from Kyoto to Hiroshima - took like 3 hours each way. The pass that lets you sit away from the rabble is nice since the cabins are virtually empty in business class or whatever it’s called
Food isn’t that expensive. Convenience stores and department stores are good options for cheaper cost food. Keep cash on you but most places take credit cards now except small hole in the wall spots. Unless they changed things, only reliable place a foreign debit card to withdraw cash from works is the post office.
“Golden Week” takes place in late April/early May. It’s a big domestic holiday week so it gets busy as citizens travel. Most major cities lots of people speak English, but they’ll love it if you try to speak Japanese (trying to speak broken Japanese helped me get past some “no English” dismissals from people, like when I tried to get a refund on my subway pass card). Tokyo subway you used to be able to buy a card and load money on it - makes subway use and transfers 100x easier. Even if you don’t like baseball, at least know about it. Especially top Japanese players - it usually gets brought up if you engage in conversation if they identify you as American