The wire type in the table is CuL and CuAg. Obviously CuL some sort of
copper wire, with the CuAg, being copper and silver (silver plated
copper?).

--------------lacquer-isolated copper wire (CuL), ------------
----------------copper-silver (CuAg), -------------

What exactly is CuL wire? Is it critical that I use it what ever it is?
Can I use plastic covered copper wire?
----------no--------------

For the high freqency coils I can easily get 2.0mm stiff copper
wire for use in electrical conduit. It comes with some sort of insulation,
probably PVC. Can I use it, and if I do, should I remove the insulation?

--------------Yes---------------