Those are some funky looking models indeed...
Test-2 and Test-4, should be quite printable...
Would it matter anything for the aesthetic/idea of the model if Test-2 was extruded down to the Y-X plane?
That is, make the model sort of a block extending upwards in the z direction from the x, y, 0 plane, rather than being a thin uneven plane as it is now.... I believe that would make it much easier to print.
Either in that same orientation or rotated 90 degrees onto its side (choose the side that results in the least dramatic overhangs)
For Test-4 you should use some support settings, or better yet, cut the model in half and print each part separately as a "hill", gluing the two parts together when finished...