Just a quick data point and stuff you already know:
I live in NYC and know first hand how quickly bikes get stolen in big cities, especially bikes unlocked even for just a few minutes "while I quickly dash in the store". I've also had a motorcycle stolen overnight from outside by home (Kyrptonite lock broken) in NYC. In-laws had their car stolen while visiting NYC. I keep my bike inside overnight and can count on the fingers of one hand the nights I've left a bicycle locked on the street overnight - even a beater - in NYC.
For decades I've used an old St. Pierre hardened steel chain with protected shackle in NYC, it weights 8lbs. (predecessor to the Kryptonite hardened chain lock). A PITA to lug around but I've not lost a bike with it. Paranoia keeps stuff secure in a big city.
As a data point, during the past decade a friend did his second cross country bike tour, east coast-to-San Fran, with his fiancée. At the very end of the ride both their bikes were locked together in San Francisco and both were stolen. Bright side is they didn't have to ship the bikes back home.
That's big cities.
As a little kid in suburbia USA, I had my bike stolen once ... I'd simply laid it down in my yard or leaned it against my house like I'd always done. Some young teenager stole it in the afternoon and the cops recovered it that evening unscathed. After that my parents bought me a chain and lock.
Never bike toured and not sure what sort of lock I'd take.
Last edited by Lovegasoline; 06-14-19 at 10:51 PM.