These circuits can be considered as semi controlled experiments that we only be content to observe what they produce carefully but not try to optimize the effect. Expensive instruments like spectrum analysers and high bandwidth scopes and good RF signal generators will be very useful to see and understand what is going on on these coils. Power extracting should not be the first goal of these circuits. Circuits gives always unexpected outputs and puzzle us keep interest on it. This for sure.
Every oddity is present.
I also recommend to observe the electrical-magnetical field inside and outside of these coil rather than the currents and voltages. I am sure you will be amazed with what you will observe and see the complexity. As these coils are not simple inductances, any parameter to change the interwinding capacitances as the tightness of the windings and enamel material and thickness the form material, isolation materials, coil leads lengths, placements of the coils on the bench, and other many other issues should be considered. The circuit and its requirements look like simple, but it is not definitevly a college class experiment. But unideal enviromnment can be thought as a advantage because generally things are discovered by accidents.