So I'm curious about Wireless charging.. This is possible for the S5, right? And also would I have to remove the back of the phone to replace with another special backing meaning I would lose the water resistance?
You can get the official Samsung Wireless Charging Back Cover that will replace your existing cover. This is the safest way to maintain water resistance. It does add a little thickness to the phone and most cases will not fit. The other option is to buy a wireless charging card that goes between the cover and battery, but this does not allow the cover to seal properly and may allow water in. I have the Official Wireless Cover and it works great. I don't use a case, I just have a glass screen protector.
Samsung also makes a wireless charging flip case with the necessary seals for water resistance. A little window displays time, weather and pedometer, and gives access to the camera.