As stated before, the most important feature of a rescue vest is the quick release system. A belt is sewn into the vest and passes through very sturdy sewn in belt loops. The belt is typically threaded through a metal friction buckle that takes stress off of the plastic quick release buckle. The belt finally passes through the plastic quick release buckle which has a large plastic ball attached making it easy to grab without seeing and pulled for fast escape. A sturdy ring is placed in the middle of the belt behind the PFD. You can attach a tether or rope to this ring. In a release, the belt slips through the belt loops and the floating ring and just the ring falls off (attached to the rope or tether). This way to don't have to cut yourself free of the rope (always carry a rescue knife anywhere that is easy to get to). Here is a short video from Zorn Outdoors describing the quick release system: Rescue Vest.
The above video covers the typical way to thread the buckle. I would call this the fully loaded option. Depending on the jacket, some may experience release challenges under lighter loads like towing a boat for instance. An alternative is threading through just one opening of the metal friction bar. This method provides far less friction than the double thread and still ensures a nice parallel entry to the plastic buckle. Unfortunately, some instructors will recommend skipping the metal friction bar altogether when towing boats. I strongly advise not doing this. For one thing, the plastic buckle isn't designed for heavy loads and may break and jam. Also, the friction bar helps to prevent a pull on an angle which can also cause a jam.