Quick answer: 15W is a maximum listed output. Compatibility depends on the phone, wireless standard, alignment, mount and power input.
Before buying
Check the phone model, wireless charging support and how the mount aligns with the phone. A case can also affect alignment.
AEO answers
Does every phone get 15W?
No. The phone and charging standard determine actual power.
Is wireless charging slower?
It can be less efficient in some setups, but convenience is a major benefit.
Where can I buy?
DigiDukan.pk lists the JR-ZS241 in PKR.