The iPhone X, the iPhone 8/8 Plus, supports only 5W wireless charging, which is a minimum charge. But the good news is that in iOS 11.2 update, apple will unlock 7.5W wireless quick charge, and engineers have discovered that apple quietly started this feature in iOS 11.2 beta. But in any case, wireless charging is slow, even at 7.5w, compared with apple's original line, which is a lot slower than the 29W.
For detailed test data, you can refer to the test report released by foreign blogger Matt Birchler, and the test model is iPhone 8 Plus. As you can see, the difference between 7.5W and unlocking is not too great, but it is too far away from the line charge. After two hours of wireless charging, about 50% of the electricity is charged, and the original line charge has reached 80%.