Originally Posted by
luv2ctheworld
In response to your first question, 2 hrs is normally enough for transiting. I've blown through there in 20 minutes without checked luggage. However, you are looking at a slightly different situation as your process will require you to go through immigration before getting your luggage... not to mention the time it takes for your bag to get to baggage carousel and re-check it.
All that takes extra time. I would recommend you try and find out if you can inter-line the luggage so it will be transferred for you instead of having you go through to re-check it.
Normally not a problem when flying the same alliance (i.e. Delta/Air France or UA and Lufthansa), but it is most likely possible.
Others here may be able to chime in on such possibility.
OP does not need to go through immigration to recheck its luggage in NRT, different alliance has no meaning that it couldn't interline luggages, it just means OP cannot get onward boarding passes.
NW of course can interline with UA. I have done plenty of interline mixing in the past, AA interline with UA, UA interline with CX, etc.