Best practice for undulating floor (metaball or continuous loft)

I'm currently working on creating a continous floor from multiple curves if they come to close they will unify into a single floor surface. I also want to use this floor to create walls from the edges by curving them either up or down.

So far i have tried to use a lofted surface which expands and meets up with the other lofted surface. The problem with these is that the lofted surface dont create a clean unified surface.

Another option that i have tried is to use metaballs onto the curves which unify when closing. Now i dividide the circles in 2 parts and draw a line between these which can then be divided into points. Using the mesh to points component i then create a surface mesh from these.  The problem with this method is that the edges are not very clean.

Do you forumites know other ways to generate a floor surface from different strands.

Or have suggestions to clean up these solutions.