I use a RAM universal finger grip mount. I've used it for years and years with my phones as a GPS. It just works. I did a 5500 mile cross country trip last year with my S4 attached to the handlebar. I made a waterproof charging setup, and simply slip a sandwich bag over the phone if it rains.
Some cases have protruding volume and power buttons, and the fingers on the mount can press those. No idea if the Otterbox is like that or not.
I tried a X-Grip. I hated that POS.
I recommend CoPilot software (or even the free HERE maps.).