Death Watch was interested in taking Mandalorian culture back to an earlier time as well.
Back then, Mandalorian armor was only being worn by Death Watch, as the people of the planet itself had become peaceful.
Bo-Katan Kryze was first introduced in The Clone Wars animated series (where she was voiced, not coincidently, by Katee Sackhoff) as a member of her own splinter group of Mandalorians, called Death Watch.
Having said that, Death Watch had no issue with things like removing helmets, so Death Watch and the Children of the Watch are not exactly the same thing.