I’m experimenting with modeling for 3d printing, and - to start - I’m exploring how to join this set of one-surface meshes together into a continuous one-surface mesh. Wondering if there’s a command to sort of automate the process. (I model a lot with polysurfaces but not so much with meshes, but I know enough to know that I would need additional surfaces to make this water tight for printing, this is a first step toward that. I understand that Rhino 8 has shrink-wrap but I’m not using it until Visualarq will work with it.) Below is an image of the surfaces in question and a close-up showing a typical joining location where the edges (in magenta) are about 1/8" apart, which is typical for this group of surfaces.
Have you tried the Shrinkwrap command?
I mentioned it in my O.P. Not running Rhino 8 yet.
Oh sorry, didn’t read that far 
If you haven’t tried Shrinkwrap, there’s a reason to still upgrade… for things like this, it works really well.
As for VisualARQ, I’ve seen a failure too just recently. Glad I don’t need it.