For the ball, arm and rail configuration, watch my previous RAM mount setup video.
The linked holder includes its B-size ball. My dashboard setup also uses a RAM track ball, a long double socket arm and a YakAttack GearTrac rail bolted down with hardware from the stainless washer kit. The short and medium arms are other size options; you don't need all three lengths. I have another RAM setup on the passenger side as well.
The Quick-Grip XL has a lot of little screws, so getting it configured the first time takes longer than most mounts.
It doesn't matter how much the car bounces or shakes, the phone does not move. You have pressure from the bottom and pressure from the top, so when it's gripped together your phone is not coming off. I've seen these on motorcycles and on ATV trails, and they're great.
Being able to adjust the screws actually makes it better: if they get loose over time, you can always tighten them again. And if you buy a new phone or a different size, the sides collapse and get smaller, so you can always adjust it.
This is my permanent setup in my current car. I actually screwed the mounts onto the car, so that's how much I'm committed to it. Definitely get it if you want a non-traditional mount.