Thanks for the feedback, and I'm glad it was helpful. I was looking for a video like this before I purchased but didn't find much so I decided to order both and put something together for others looking at these magnifiers.
Can I please check with you whether you need to have the Leica M thread adapter to allow either of the 1.25x and 1.4x the magnifiers to screw onto the viewfinder?
Yes, you need the thread adapter if you have a Leica M10 or any variation of the M10. The previous generations of the Leica M do not need the thread adapter.