Any iphone case that allows wireless charging on a charge-mat will work. I've found that most otter-boxes are too thick to allow for wireless charging. Make sure the case you buy specifically states that it will not interfere with wireless charging. Those gel-skin cases usually work, but only protects against screen scratches and very short drops. It's better than nothing - IMHO.
Is this for an iPhone with wireless charging built in or a case that adds wireless charging to an older iPhone? If you have it built in you'll want to find a thin case that won't block the wireless charging in some way (metal, too thick, card holder etc) and even then it can depend. On my Samsung S10 I use a thin tpu case and I positioned a magnet for my magnetic phone mount so it doesn't interrupt the wireless charging. It took a little trial end error to get it in the right spot so the wireless charger in my car and the one I use at my computer desk both worked. The wireless charging pad in the prime is low powered so I don't use it often, I have a quick charge 3.0 cigarette plug thing and use wired charging when I'm driving. Wireless charging won't keep up if you're streaming music and it can heat the phone up especially on warm days with the sun baking the center tray area
Yep; I use the rear USB charge ports instead of the one next to the lighter for charging - they're at 2A vs the 1A next to the lighter and the factory installed wireless charger.
Yup the usb in the front is also very slow charging. And it's the one to use carplay, right? Can it even keep up if you're streaming music and using maps?
Yes on the port; No on the phone charge. You'll actually be lucky to have the same SOC when you disconnect. Every trip, more than an hour long, I'd loose about 2%. If you lose cell tower connection, for any amount of time, the discharge is even worse.
