Forget to answer this part. Tactically you're always in a better position if you're behind the subjects vehicle. I know pulling in front makes more sense to prevent a pull away and car chase but it gives the bad guy an equal shot if he pulls out a gun. If you're behind he has to get out and turn to shoot you with no door to protect him from return fire. The police vehicle should also be slightly canted so that the front of it will also offer some protection.
I'm not sure what you're referring to with regards to handcuffing him at the trunk. I'm not sure I've seen all the videos in their entirety.