This is a good question. I would offer that there are at least two major types of soy sauce: light and dark. They are used in a variety of ways in Northeast Asian cooking (Mainland China, Koreas, Japan, Taiwan, Hongkong, Macao). For example, when you steam a fish (southern Chinese/Canto style), you use a combination of light and dark soy sauces. (I have no idea why, but this is a traditional recipe taught to me years ago.) Soy sauce has two primary "taste" components (previously I discussed visual components): (a) the fermented soy beans and (b) the umami (MSG/monosodium glutamate). Even if you feel like (a) is overwhelmed by your cooking, it is still enhanced by (b) which, for most people, makes any savory food taste more appealing.
For me, nothing beats raw fish (sashimi or sushi) as a taste test for a soy sauce, but I frequently use a mixture with Japanese ponzu... so ignore any expertise that I have on the matter! I am sure that each culinary region in Northeast Asia will have a different answer. You could probably interview 100 chefs from the region and get 25 different answers.
Lastly, there is a third type of soy sauce used in Southeast Asia called sweet soy sauce, or kecap manis in Bahasa Melayu/Indonesia.
Surely, "salt" has to be mentioned when talking about the primary taste components of soy? Normal soy is around 17% salt, which is a lot and really plays a part, in my opinion.
Fun facts, the Malay word garam for salt most probably come from the Roman word Garum, a very popular fermented fish sauce from an ancient Malay Champa kingdom [1]. The Champa kingdom used to rule majority of Vietnam and the South China Sea used to be called Champa Sea even in ancient Chinese chronicles [2]. If I'm not mistaken the Vietnamese themselves still calling this particular fish sauce as Champa fish sauce, while the rest of the world call this Vietnamese fish sauce [3].
The original world from Old Malay for salt is probably "asin", that's now become the word for taste of salt or "masin" meaning salty.
Soy sauce is meant to largely replace the salt component of your dish. If you're using so much that it's particularly salty, you're using too much.
Way back in the day, when salt was scarce and expensive, the whole point of stuff like fish sauce, miso, soy sauce, etc... was to provide salt but also cut it by adding other ingredients.
For me, nothing beats raw fish (sashimi or sushi) as a taste test for a soy sauce, but I frequently use a mixture with Japanese ponzu... so ignore any expertise that I have on the matter! I am sure that each culinary region in Northeast Asia will have a different answer. You could probably interview 100 chefs from the region and get 25 different answers.
Lastly, there is a third type of soy sauce used in Southeast Asia called sweet soy sauce, or kecap manis in Bahasa Melayu/Indonesia.