A friend wrote to me recently that he is trying "micro" leaders for nymphing with a 4x (0.16mm) sighter section. For most of my fishing however a 4X sighter is more of a "macro" leader these days. The size of trout I normally chase allow me to go lower and benefit from the many good sides of this approach. I do fish 4x and higher when I get the chance to target bigger fish. Given the numbers of anglers practicing nymphing techniques around the globe I can imagine that the worlds "micro" and "macro" can mean very different things for different people in different conditions. My choice is to avoid them altogether when speaking about leaders. After all we already have several systems (inches, millimeters and fly fishing's very own X system) to define exactly what the diameter of a leader is. A "micro", "macro" or just nymphing leader is built following the same principles, anyway.
In my 20 or so years of studying and practicing nymphing techniques I had the fortune to fish with and learn from some of the world's top rods from Spain, France and Czechia. One key thing I learned is that regardless of the variations of technique, when fishing on a tight line they all use essentially the same leader formula. The diameter varies depending on the conditions but the rest stays the same. The lowest one can handle is usually the best: how low would depend on the fish and their strength, on the specific water fished (the chance of breakages because of snags, for example), on the quality and capacity of the equipment used and the skill level of the angler. Not all nymphing rods get properly loaded with lower diameter leaders and light nymphs, and not all anglers can cast those without the right instruction and some practice. Reaching my Spanish friends' skill level in working tiny, light nymphs at a distance is something I keep working hard on. Progress is not exactly fast but the patience and effort are worth it and the results quite rewarding.
Here is a link to a video where Ciprian and I share what we learned from our European friends about nymphing leaders and how we adapt and use this in our own fishing. I promise, we don't use the words "micro" and "macro". Frankly, we don't quite like the term "Euro" either - after all in Europe it is just nymphing - but we can't be perfect after all ;)