I suspect the data transfer requirements of CarPlay can be handled by USB2

Exactly. If you look at YouTube bitrate for a 1080p video, it's 8mbps, which is 1.67% of the theoretical max data rate of USB2 (480mbps), so there's more than enough bandwidth for CarPlay.

Yeah USB3 and greater is really only needed for high res displays and faster large storage.

given that carplay has, until now, been exclusively implemented by devices that don't support USB3, that's a pretty good suspicion

Since CarPlay has worked for years over Lightning cables, 2.0 speeds must be sufficient

CarPlay is wireless for some brands of car, wired for others.

My Prius has wired carplay (which makes the Qi charger seem absurd, although as it turns out the Qi charger doesn’t work most of the time), so I bought a $50 box that plugs into the USB port and gives me wireless carplay.

Which one did you get? I've been looking to get one recently but have heard that they're kind of a crapshoot and not very polished in UX.

This is the one I have http://www.amazon.com/exec/obidos/ASIN/B0B8RKXK9R/donhosek

It’s been in use for a year with not a single issue. I set it up with my phone and have been able to forget about its existence ever since.

I got a generic "ATOTO" one that was on sale. I had to upgrade the firmware since there was some audio stutter after about 15 minutes, but after that it's been just as stable as wired CarPlay for me.

I just got a carlinkit 5.0 and initial impression is that it's working great with very little latency. Can't speak to long term reliability.

Should also mention I bought mine via this deal for $40

https://slickdeals.net/f/16869551-carlinkit-5-0-cpc200-2air-...

As far as "not very polished UX", after connecting it's been nothing but the standard CarPlay interface. The instructions say there's a web UI accessible via wifi where you can install updates or change configuration but I had no need to use it. Just connect with Bluetooth, wait a second, and accept the "Connect to CarPlay" popup.

I've got a Quadlock for my Audi and I'm returning it, disconnects often.