Opinions differ on batteries and 100%. First, the swelling comes from contaminants in the chemicals in the battery, not from any use pattern. And the contaminates can be as small as a few hundred atoms. Over time the Lithium is converted to Hydrogen and that causes swelling.
As for battery life, Lithium batteries "prefer" to be between 80 and 40% for optimum life. Going below 40% is very hard on the battery as the chemical reactions get exercised a lot. Staying above 80% is not that hard, certainly not as hard as a deep discharge. Most battery manufacturers rate the battery slightly below what it can actually handle and then work with the charger to stop at a reported 100% that really isn't 100% of the physical battery, just to keep the battery from being "fully" charged. But not all batteries play well with all chargers, so it's safe to assume that 100% is 100%. That said, staying at 100% is not that hard on the battery life in the long run. My MBPr is rarely off the external power and my battery lasted 4 years before swelling got to it, and the new battery is just fine now in the second year of service, on mains power 90+% of the time.
As for the video you watched, I don't know what the "button" or "ring" you may be talking about, but in the case of the battery pushing up on the trackpad, what my wife saw was uncontrollable cursor movement and no clicks (she couldn't press down hard enough to overcome the battery pushing up. New battery and the issue went away instantly.
Once you get a screwdriver to open that machine, just touch the battery. The outer cover of the battery should be a tight fit to the battery itself. If it's puffy at all, it is swollen.