You might damage the other end of the connection if the 5X considers it alright to draw 3A (because the cable says so) but the other end isn't prepared to deal

You might damage the other end of the connection if the 5X considers it alright to draw 3A (because the cable says so) but the other end isn't prepared to deal with that. Generally speaking, USB cables won't make the receiving end request more than they can handle. It's always about the power source.