I asked about the differences between Lee Kum Kee soy sauces, and got lots of answers:
"Chinese soy sauce is made of 100% soy. Japanese soy is made of a mixture of soy and wheat. Light soy sauce is for flavouring your rice, or adding to your already prepared food. Dark soy sauce thicker and a bit sweet, mainly for adding color... the premium stuff is often labelled as such because it's the first batch harvested after the fermentation process . They kinda treat it like whiskey. Each subsequent harvest lowers the "quality" and cannot be labelled premium. Kum Chun is made with wheat." (I looked at the ingredients of the "premium" version and it has wheat flour, so)
"A lot of people seem to not know this, but light soy sauce actually tastes saltier than dark soy sauce due to the sugar and stronger soy flavour masking the salt in dark soy sauce. So don't let the colour and viscosity fool you when thinking of what soy sauce to use."
"“Premium” soy sauce is LKK’s original. “Kum Chun” is their cheaper “value” option, I suspect to compete with the more affordable (mainland) Chinese brands. Lower soybean content (Premium is about 17% as per their website). Theoretically there would be a difference in taste - less richness/depth, more straight saltiness or even MSG umami. Whether it makes a difference depends on your palate and what you’re using it for.
There are also a few cheaper grades you can sometimes see in Asian supermarkets - these are usually in Chinese packaging and are mainly tailored to HK/PRC local markets and foodservice."
"Basically:
Dark soy = thicker, sweeter, has added molasses, has more sodium & sugar. Used for braises and marinades.
Regular or light soy = thinner, lighter colour. Good for everyday use.
Premium = “first press” (the virgin olive oil equivalent of soy sauce), more complex flavours than light. Think of it as Light+ I suppose?
I think Kum chun is the same as dark soy...
superior is a kind of light soy. Looks like it has less ingredients and contains high fructose corn syrup + sweetener instead of sugar."
"At least within Chinese brands, any soy sauce is usually a type of “light soy sauce” (生抽) and can be used in most cooking applications interchangeably. Different variations (premium, kum chun) won’t really change ur dish too too much unless u are somehow using huge quantities. Just don’t use “dark soy sauce” (老抽) as a substitute where any recipe says just “soy sauce” or “light soy sauce.” Dark soy sauce has a very strong flavor and is usually used to mainly add color. A lot of Chinese ppl will also use Japanese soy sauce as their go-to soy sauce/“light soy sauce,” since Japanese soy sauce tends not to have any characteristics that will clash with dishes across many cuisines. U can also use tamari as someone else mentioned, but it is noticeably richer and darker in color (though will not destroy a dish like dark soy sauce would)."
"Your normal soy sauce is medium-dark so it’ll be slightly sweeter with a more mirin-like flavor. It’s not to be mistaken with light soy sauce AKA soup soy sauce"