Baking with Cage

#1

Hello!
Just started to learn Maya, the question is: there is a high-poly model of the house, and I use Cage to bake the normals to a low-poly.
For this, accordingly, I unwrap the low-poly model (in the UV-editor, the “Cut” operation on all sharp edges, then, I think, the “Layout” operation, so that it automatically all spread without intersections). After the Cut operation, my vertices are duplicated in the UV seams.
When I try to make Cage from this model and scale Cage so that it overlaps the high-polyl model (for that I move the vertices along their normals, fattening my Cage), my duplicated vertices (in places of UV seams) “fly apart” in different directions, making Cage torn in fact.
Maybe I misunderstand the unwrapping mechanism, maybe the vertices should not be duplicated (no, technically, of course, they WILL BE duplicated) at least in the 3D editor itself? And what about the Cage, because its topology should completely coincide with the topology of the original model, I can not combine duplicated vertices.
In general, I apologize for, perhaps, stupid questions.
P.S. At the same time I would like to know why the Layout operation (in the UV-Editor) makes some edges hard at its own discretion? In general, I watched many tutorials, and I do not understand, how to unwrap the model simply just using my UV seams. Without any automatic conversions.
Thank you in advance!