I decided to try out the Japan Customs app and automated gates on my trip to Tokyo last week. You input the customs form information on your smartphone and get a QR code. Then you scan the QR code and have your picture taken by an automated kiosk in the baggage claim area. Then you go to the exit gate, get your picture taken again, and walk through.

Cool idea in theory, but pretty useless in practice. Doesn't really save much time. You have to remove your mask for both photos, which is an extra pain if your hands are full with luggage. If you are traveling with family, it actually takes more time because each passenger has to separately register. I might try it again if I'm entering solo and Japan has done away with its masking demands, but until then I'll stick to the paper form.