The ProClip is the best mounting system for any car. It's expensive, but really worth it. You need to order the car holder (which is made specifically for each make/model), and you need a phone holder. I have a case on my Note 4 (but not an Otterbox), and it works great. For the Otterbox, you'll probably need the largest of the universal phone holders. EDIT: I just checked on ProClip site and they have a mount speciafically for the Note 4 with an Otterbox Defender: http://www.proclipusa.com/phone-hol...nstallation-513694-19764.cmsv?p_leftorright=0
The above is just the holder. You then have to get the proper car mount. As I said, this is an expensive solution but one that I have been using for many years because it's the best and most secure car mount that I have ever used.
This iBolt mount is a very well liked cell phone mount for vehicles. I have one and 2 prior versions over the years and have nothing but "good" to say about the product. This mount should hold your phone and otterbox and a quick contact to the company should confirm. I only use by Note's naked so don't have first hand knowledge. Amazon.com: iBOLT xProDock Connect Kit Universal Car Holder: Cell Phones & Accessories
The Scosche MagicMOUNT is great for me. Holds my Note 4 and Z30 easily and on any angle. Never had a problem with them. My Note 4 has a Seidio Surface case on it too.