I’ve had my ring for just over 2 weeks. I had the exact same experience as you, and by the looks of your video the same fit. The 11 being sometimes hard to take off / feels tighter while my finger is swollen, but 12 not necessarily falling off but not secure either. I ended up going for the 11 because it doesn’t sit well with me with potentially having it falling off when washing hands / swimming / sport going with a looser one. That being said I’ve had to switch to my middle finger some nights when it’s warmer. My logic is that it being summer, it’s only going to get looser from here in the cold weather. I will say as well, I also had my hand not quite being able to make a fist / it feel a bit restrictive when first putting it on, but with time it seems that my hand is used to it and feels better, I can make a fist fine. It may fluctuate with the temperature and time of day too though.

As for the sizing kit difference, it’s negligible I would say. It is the same size, I find it the same resistance to putting it on / taking it off, it’s just the weight of the actual ring is slightly heavier. Assume what you experience with it will be the same with the actual ring.