I was there in for several months in graduate school doing research for my thesis, wasn't part of a tour. Based out of Kim Il Sung university at the time. I spent about a year in South Korea as well prior. Since I wasn't on a formal tour, I was left to my own devices a lot of the time unless I needed a guide to help me get access somewhere.
Technically yes, every rural farming village could have been secretly micced with hidden cameras on the off chance that a foreigner was going to stop by, but that seems unlikely. This was a little over ten years ago so cell phones (which would be a fairly common metric of government surviellence) were not as prevalent in the DPRK yet as they are now, so a lot of people weren't carrying one. I was a no-name graduate student, not a well-known diplomat, I don't think the government was particularly invested in spending large sums of money tracking me. So yes, technically they COULD have, but just as much as any other state could have.
Japan, you usually use "Taro Tanaka" as the goto placeholder name. Tanaka is a very common surname here and it's super easy to write as well (田中). Sato is actually the most common but also a lot harder to write (佐藤). Tanaka is also a very "working class" name, it litearlly means "in the rice field" and most likely comes from families with a background of rice farmers. Taro also a very common given name; there have been quite a few Taro Tanakas throughout history despite being the placeholder name on most forms and the like. Taro, incidentally means "Big/Strong Son".
I am not sure offhand of a female equilvalent, it's usually Taro as the placeholder.