As discussed above, they aren't idiot-proof, and you should definitely practice a bit and cut some open. But I think it probably is still an easier process to get started with, if not to master, than either fillet-brazing or TIG. Have never tried fillet brazing (or lugs but have done a bit of silver soldering) but I know that it took me many many hours of practice and making other projects with the TIG before I was ready to try making frames. The difference is TIG happens very fast and goes wrong very fast. This means you need the practice because there's no time to think on your feet.

There were recently a couple of videos on Henry Wildeberry's channel where he made a pretty decent lugged frame. I think he probably had a bit of training from John Fitzgerald, he dropped a lot of silver on his feet, and a few joints he actually took apart and re-did. But it all worked out pretty good in the end (and he did a really nice job on the ends of the seat stays). I recommend watching those, not as a how-to guide but to get a sense for what it's like as a beginner.