I've travelled on this route passing through Xiamen to Tokyo last year.

Airline is quite decent however Xiamen is a proper headache of an airport.
You will indeed need to pass immigration and recheck your bags.

I spent a good amount of time explaining to the immigration staff what a transit visa is as that gate was closed when I arrived there and the staff did not understand. But in the end they gave me (and the rest of the flight) the 72 hr transit visa.

Layout of the airport isn't great either, the international departure (to recheck your bags) was poorly marked and quite a walk from arrivals.

Also a note to keep in mind, avoid typhoon season. This is dead centre to most of the heat and if you travel during the season I'm quite certain cancellation %'s tend to be quite high.