I'm assuming that the content id is how coins work, 'cause if you use a different region game than the region your profile is set for, it will error when trying to redeem coins. beyond that, I don't understand why every game seems to have a different content id despite region if they're essentially the same game. it's much harder to get a specific region with Nintendo and Xbox consoles, since the games have to be dumped from the system. Sony's servers can be accessed on the pc without risk of ban, and there have been several people who've made databases for their content.
so far, I've found one game in my nsp folder to have a different content id than the update. the content id is in the file, near the top, followed by several 0s. I assume that that's where that id comes from when renaming, and the third number from the right is how it determines game, update, dlc, but in a lot of cases, it can't determine game name. I don't know how all of this affects one another even for a region free system.