Question about Xiaomi 15

In general, the devices negotiate what they can do with each other. So unless you use something exotic / homemade, you should be able to use any USB power source - some will charge slower (5V 1A), others faster (20V ~5A).
By the way:
In the settings, under Battery, Charging options, Wired charging mode, you can choose between "Standard" (saves the battery) and "Top speed" (if you need to go faster).