NW / KLM connections in AMS are generally very easy.
Checking in at EDI, KLM will be able to check luggage all the way through to BOS and print boarding passes for both segments. NW/KLM are very well integrated across the Atlantic.
In AMS, arriving from the UK you will have to go through passport control. Then prior to getting on the flight to BOS, you have to go through security at the gate, as with all flights in AMS. 1:20 doesn't leave any time to hang around, but it is a very do-able connection. I do it routinely.