Are all of those PCs connecting to Overwatch? If not, that info would be irrelevant.
Assuming you’re playing on the Singapore server, the problem lies between your home and the Overwatch server, which requires a submarine cable in the middle to make the connection. Other services or software may not rely on that same cable because they are hosted in different parts of Singapore or entirely different countries.
Comparing a connection route to one game has absolutely nothing to do with connections to other services or games. This situation is explained twice in the sticky threads: