I’ve encountered this term in this video. I tried looking up guest soap on the internet, but I only got information about buying them. Are they soaps for guests in the USA?
Guest soaps simply means soap bars that are supposed to be used by guests staying at a particular place such as someone's home. In the context you provided us with, in that clip, they're talking about soaps that are used only when guests are visiting their place. The idea is that guest soaps typically look nicer and are usually more expensive (at least, look more expensive) than regular ones. So, you only put those out on a special occasion such as when you have people around. There is no special meaning. Guest soaps are literally what they are—soaps for guests.