I use the Infiniapps Magnetic CD slot mount. It's not designed specifically for the Nexus 5, but it's not bulky or a hassle to use. Also, since the plates in the phone line up well with the magnets in the mount; you don't need to clamp it or anything. Just put the middle of the phone against it and it holds in place just fine. Portrait or landscape isn't a problem. No problems on bumpy rides or anything either.
I personally won't use Qi chargers in the car, as I use navigation a lot and stream music all the time. Don't want to have problems with heat. This mount doesn't get in the way, just pop in a USB cable to an Anker car charger and you're good to go.