I did not work as an electrician in Europe, but I did other work, and traveled extensively there, back in the 80's. My travels took me to many places, on both sides of "the wall," as well as other places along the Mediterranean.
It's hard to make any "perfect" statements. Things do change over time, and each area has its' own differences. I tried to describe a common European method in terms an American would understand.
I saw quite a few boxes that no longer sat tight to the wall, and had some movement. Even completely loose boxes had their movement limited by the wires coming in to them.
You're quite right about the tubing being placed in the wall. I have never seen an American job where the electrician did what I often saw done in Europe: using a demolition hammer to carve a trench in the wall to set the tubing. The trench was then filled, as you said, with plaster.
The double-blade saws used in Europe to cut parallel grooves in masonry - blades are set about 3/4" apart - are all but unknown here. While it it possible to order one from Flex, Bosch USA told me to forget about buying one of theirs.
I like Wagos. I have only rarely seen them for sale here, though the similar Ideal "InSure" product is often seen on shelves at the parts house. I have yet to encounter one in the field that I did not instal myself.
Personally, I like the Wagos with the little levers. You can remove wires from them. I have to special order mine from a Wago distributor far from my home.
