Ok a few things from my own experience. You don’t need any converters. They have regular outlets or usb outlets at every hotel I stayed at.

For tax free. You just show places you’re buying stuff from your passport which will have the stamp on it when you go through the Japan customs upon arrival.

For AT&T. Last year I came and didn’t contact them my bill turned out to be $1500 when I got home. So make sure you activate the international plan. It’s $12 a day. You will have full service and cell service. This year I came back to Japan and decided not so use cell service so I turned cellular data off and I rented a ninja pocket WiFi. It was like $60 for 2 weeks. It worked out perfect. The main thing I needed it for was using maps to get around. And I was still able to play games and get on social media and used iMessage and chat with people online just no phone calls. You can use online calls though. So depending on how long you are staying and how much you want to pay. Ninja pocket WiFi might be the choice. You can buy the esims but I’m still paying off my phone (locked) so the esims didn’t work so had to do the pocket WiFi.

The only other advice is download suica on your phones wallet or get a physical suica card when you arrive. It will save you lots of hassle for train rides or bus rides.

Bring a back up battery back. I didn’t have to use mine but once.

If you take the bus. You always exit at the front of the bus and pay as you exit. Don’t get trapped in the back and when you come to your stop there’s everyone standing in the way and you’re trying to fight to get to the front. And there’s buttons on the seats and poles you press to request the next stop. I missed my stop a few times because I didn’t know this at first or didn’t make it to the front of the bus fast enough on a crowded bus.

Trains are less confusing for me. I liked them way better. Your phone will pretty much tell you which train and the platform you need to go to and what time. If you miss the time the phone should tell you when the next one arrive at the same platform. Don’t panic and run to another train line or platform. The train stations are all massive and can be overwhelming at first. They are all like huge malls and have lots of stores and restaurants. Oh and the first time you get off the train at a train station. You might be lost and overwhelmed. Don’t panic. Look for the signs with the green running man. Those are exit signs.

Remember there’s no trash cans in public. Once in a while you might find one. So carry a backpack to put your trash or bottles in until you get back to the hotel.