I’ve got the Freestyle Libre (the white disc in the first pic in your post). I find it incredibly useful. I use it intermittently, several times a year, for two weeks at a time. It gives continuous blood glucose readings 24/7 for those two weeks, allowing me to properly understand exactly what effects my sleep, sleep deprivation, food, drink, exercise, fasting, stress levels and so on have on my blood glucose.
I’m not type 1 or an uncontrolled type 2 diabetic, but I have seriously wacky hormones and reactive hypoglycaemia which have, at times, pushed my blood glucose up into diabetic levels even while Low Carbing.
The joy of using the Libre is that I get all the info I need to tailor make my own personal way of eating. It taught me that I am gluten intolerant. Even tiny amounts of gluten would trigger hypos. It also showed me how to time food and exactly what happens to my blood glucose during fasts - and why I hit a wall with the longer ones.
It is too expensive for me to justify using it all the time, because my blood glucose is now under good control, but as a learning tool and for occasional maintenance, I cannot praise it enough, and would recommend that anyone with a deranged glucose metabolism tries it for a few weeks as a learning tool.
I’m currently using it to see what effect ZC is having on my glucose levels - and it it proving to be very interesting. Definitely not what I expected!