CarPlay works way better over WiFi, and USB connections are now deprecated by Apple, which means all new CarPlay features will only be supported by Apple on the WiFi interface, not the USB one. This may well be a problem depending on the version of your Apple device and the version of your vehicle HU. .... the newer it is the more likely it is that WiFi will provide a far better experience.
I have a 22MY Ocean and connect CarPlay wirelessly to the Access Point provided by the Discover Media head unit. See below.
View attachment 175987
USB is a dreadful data interface for use in cars. The reason is that normally a USB connector is soldered directly to a circuit board in a PC or Laptop and it is a matter of millimetres from the USB connector to the USB Host/Hub hardware in the PC/Laptop. Then the USB device either plugs directly into the USB socket or it has a single cable, usually no longer than about a meter (dependent on required bandwidth).
This is not the case in a vehicle. There is an extension cable in the vehicle wiring harness from the host device (the head-unit) to the USB connector in the car. Then there is another cable between the vehicle USB connector and the mobile device.
For the high frequency communication required to get the video data from the iPhone to the Head unit this is a very sub-optimal solution, to put two cables together, where the customer chooses one cable, and the vehicle manufacturer chooses the other - you end up with impedance mis-matches and multiple connections in this setup which the USB protocol works round with re-try mechanisms. This slows the throughput of data and can cause the USB connection to reset - hence the advice to use a high quality cable, usually from the auto manufacturer.
New CarPlay features, particularly the support of multiple screens (Main display, Instrument cluster and head-up if fitted), require data throughput that this USB setup simply can't provide reliably, hence the move to wireless.
Part of my job was the introduction of USB to vehicles and when you put the USB signal up on an oscilloscope it is very evident that the communication can be severely disrupted by the cable, device connector condition, the quality of the connectors, and the quality of the attachment of the cable to its connectors.
In short, USB is yesterday for in-vehicle connection to smart-phones.
PS: I plug my phone into the charging socket on the end of the kitchen block and put the phone in a pocket on the back of the seat - run everything wirelessly on both my Android(Samsung) and iPhone.