* currently everyone wears masks everywhere all the the time. There are stores here and there that sell masks in a variety of styles, so you can color-coordinate with you outfit if you want.
* submit your vaccination card before arrival. Otherwise you are going to be in a long line.
* all iPhones since the 8 have native Suica support. You can add it in the wallet up. It’s the fastest way to use the train and pay for stuff in general. It has fairly wide acceptance for lower value transactions: vending machines, convince stores, restaurants, taxis.
* for faster internet, you can get an eSIM before you go. This is much easier and cheaper than buying a SIM on arrival. Having faster network access is handy for checking train schedules and using QR code ordering systems that are in some restaurants. Try not to read hacker news all the time ;-)
* bringing large luggage on trains is a pain (stairs in stations, crowded trains, limited baggage area in reserved trains (besides Narita Express)). Carry on size is ok. If you need the large luggage for a long trip to Tokyo, it’s probably easiest to take a bus from the airport to Tokyo City Air Terminal (or the Yokohama version) and then a taxi or Uber Black to your hotel. Then use a duffel bag for trips further out like to the beach or a ryokan. An advanced option is using a mail currier between hotels and the airport, but I have not personally tried that way.