The main building has 4 floors. You will exit customs on the 1st floor. On floor 2 is domestic departures and several restaurants, many serving Japanese food. Floor 3 has several more restaurants and shops. The restaurants there might be a bit nicer in general, but not what I would call extremely expensive. Floor 4 is international departures. On floors 2 and 3, you should have several choices of typical Japanese food.

The foreign lines are often much shorter than the Japanese ones. It depends on the time of day and if another plane full of foreigners has just landed. I'm usually arriving from the US, so my arrival times are typically 4-7PM. I have permanent residency, so get through in a couple of minutes. But, I don't think that the other foreigners have to wait much longer. I think that if you had to wait more than 10 minutes I would be shocked. It's not an extremely busy airport.

Departure security and immigration are also quite efficient. If you are close to departure, just tell them your flight number and they will personally escort you through.