I know the Abbe Georges de Nantes wrote a scathing liber accusationis against Paul VI, and another (not as well done) against JP2. He seems to be (or to call himself) traditionalist, yet I believe the Abbe says the NOM. Beyond that, I know little.
I do not believe the Abbe de Nantes (nor his group) was ever a sede-vacantist, although he provides much good evidence for those who have adopted that position. From what I have seen, in the early days he was hammering, but in a more precise manner (and he was spot-on with much of what he said). As he has gotten older, his hammering is just not nearly as precise, so it can leave a bad impression - perhaps vitriolic, etc.
Yes, I knew about their adherence to monarchism. They also have the claim to be communitarian as well as Catholic in the Phalange. I have read some of the 150 Points of the Phalange on that site. In fact, I printed all out and have it in a binder. :D