I'm not sure if this helps, but when I did my European double-crossing (Bulgaria-France-Black Sea with sizable detours) in 2014 on the Raven Tour AndyBG so kindly loaned me, I used his Kryptonite Evo-2000 U-lock and a 10mm vinyl-covered cable to secure the bike. I was very "careful",
ALWAYS locked it and parked with care and concern and had no problems. I didn't lose a single item to theft or pilferage, but I put that down to my care and generally nice people.
In my experience, theft is a generally greater problem in larger places. I felt less comfortable parking the bike in larger places like Belgrade and Bucharest and moreso in small villages.
I only had a couple "concerning" moments. One was at a museum in Romania. A young boy known to be a problem in the area kept hanging around the bike and when one of the staff saw he was there making me uncomfortable about entering, she voluntarily brought a chair and a book outside and read next to the bike while I toured the museum with the docent. Of course the bike was also locked, but I cannot think of better theft prevention!
First photo below shows the bike "fully dressed" at the beginning of my tour at Andy's place. I brought and fitted my own seatpost, stem, chainring, pedals and luggage/contents so the 587S RavenTour fit like my 590M Nomad at home.
Second photo shows the bare bike parked next to my dining bench at a "rustic" restaurant in Romania on a little jaunt I took after unpacking at my lodging near the end of my journey. For this, just the U-lock through the frame and rear wheel were enough to reassure me the bike would not fall victim to a "grab-and-go" theft while I was eating next to it.
I have to and do take much greater precautions here at home. I think the risk depends very much on where you ride, timing and circumstance.
Best,
Dan.