many factors involved here
1. charger amperage
2. cable transfer amperage level
3. cable fast charging capability
4. phone charging capacity
like my mi3, max input is 2A, when i use my own fast charging cable with fat lines only can get around 1.8Amps. (my charger size is 5A)

1. if your phone detect is normal USB cable, then is 0.5A
2. if your phone max can charge at 1A, then if you use 2A charger and 2A cable, you will end up with 1A only.
3. fast charging is just a difference with the pinout where they shorted one of the data pin, your phone will detect this difference and allow more juice than 0.5A to flow in.
4. some of fast charging cable copper core is very thin, so can support around 1A only. good cables is thick on the core, with shorted pins to enable fast charging, and braided to prevent snapping when bent