You’re totally right – for objects without hard surface normal maps it’s definitely best to use as few seams as possible. From what I’ve tried it’s not usually worth it to make a separate unwrap for the other textures because #1 it increases the file size of the asset and #2 the second unwrap will still have a lot of seams since by nature the object is made up of a lot of sharp angles anyway, so it will only be marginally better.
You shouldn’t notice the seams when painting across shells in Blender or Substance, but it will mess with tiled textures if you use UV projection instead of Triplaner projection.
