Isocurve issue

Hi there, as an inexperienced user, I’m  having some troubles here.

I’m starting with two surfaces.

My goal is to get the isocurves of the two surfaces, the isocurves of the surfaces which would be in-between the two existing surfaces, and the isocurves of the surfaces which are in-between the U’s and V’s of the existing two.

I’m unsuccessful in a couple of things:
- Now I’m using the SubSrf Isotrim, which I think makes the definition heavy and, for now, I don’t need the isotrimmed surfaces, but just the isocurves.
- The other issue I can’t solve is that I sometimes have two surfaces as inputs which have a different surface plane (like srf 3 in the rhino model). What happens, is that the lines in-between the two, are twisted.
- And the third, more general question, is: How can I turn trimmed surfaces into NURBS surfaces (in rhino or grasshopper), so the Divide Srf component works based on the edges of the surface, instead on the edge of the untrimmed srf.
I know the following works for one trimmed surface, but I guess it might be a bit overdone (and doesn’t work for multiple surfaces): Input trimmed srf > Explode Brep > use the vertices > exploded in four outputs > use them as input for Srf4Pt.

Still in the learning process  so please tell me if I do things which could be done must easier. And thanks in advance!