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.