It can be mixed.
Even if the phone does not support fast charging, it can be charged with a charger that supports fast charging.
Now many mobile phones support fast charging, the difference is that fast charging specifications are different.
For example, some mobile phones support 65W fast charge, some mobile phones support 18W fast charge, and some mobile phones support 40W fast charge.
When charging, 40W fast charge is the use of 10V\/4A charging mode, Apple's 18W fast charge is the use of 9V\/2A charging mode.