The iPhone 8 and later models can fast charge one of two ways.
The first is via USB-C that supports USB Power Delivery, using a USB-C to Lightning cable. They have a draw limit of 15W (9V/1.67A). That’s built into the phone. In general they don’t actually draw much more than 10W unless the battery is nearly dead and you’re using it with heavy power demands.
The second is via USB-A that supports Apple 2.4A, using a regular Lightning cable. Apple 2.4A is an outdated, but still in play, fast charging standard Apple made before USB-C. That has a max draw rate of 10.5W. In real world practice USB Power Delivery charges faster if the iPhone’s battery is between 0-30%. The gap between the two narrows as you approach 50%. And by 70% both fast charging standards stop and normal charging kicks in.
Most of Anker’s USB-A ports support Apple 2.4A. So this new charger will fast charge the iPhone up to 15W via USB-C (but probably closer to 10W if you measured it at random). And probably up to 10.5W (buy probably closer to 8-9W measured at random) via USB-A. If charging overnight the difference doesn’t matter. If charging for only 30 minutes you’ll probably get more charge via USB-C.
The iPhone charges more slowly than most current Android phones with USB-C. Even with the most ideal charger and cable setup.