Does Harmonic Wobble create sideband frequencies? What exactly does Feathering do to the frequency feathering is applied to? How does any of this effect what is signal available at the various output terminals of my spooky boost 2.0?

When you transmit a freq, depending on the waveform you're using, you're transmitting also a number of "echoes" (harmonics) along with the main freq.

If you are using a sine waveform, then no harmonics at all, and only the main freq being transmitted.
There is no way of changing the harmonics being transmitted other than change the waveform used (or modulating the signal).

Here you can see what the spectrum looks like when transmitting 1,000Hz using several waveforms:

MM_PulseMix4

Sine Waveform

Harmonic Wobble, or Feathering, do not alter the harmonics present whithin a freq. What they do is altering the main freq itself (and thus all the harmonics that naturally go together with it due to the waveform used). This alteration is harmonically related to the main freq, so you can choose, for example, that instead of a freq of 1,000Hz, you get 1,000Hz 2,000Hz 4,000Hz 2,000Hz and 1,000Hz if you select Octave 4 Stage Wobble.

All these freqs are harmonically related, and each and every one, when transmitted, will have some natural harmonics, depending exclusively on the waveform being used.

When you use a 100%offset with a square waveform, the harmonics you get are similar (but not exactly) to the ones you get using 0% offset, but with lower intensity, as you can see with these two graphs, one for the square waveform, and the other for the MM_Modsquare, which is a square waveform with a 100% offset inside, and a Duty Cycle of 61,8%:

Square Waveform

MM_ModSquare

If you use a freq on Out1, and another freq on Out2, what you get is the sum of the two when you use the boost device.

No sidebands appear, as there is no modulation, and so, no carrier at all. For a freq to be a carrier, it must carry something, and that is done using modulation. Spooky2 unfortunately can't do modulation (except if you use Spooky Central).

So Harmonic Wobble can't create sidebands.
You can "emulate" sidebands using certain waveforms, as Damped Sine, or H-Bomb, as you can see on their spectrums when transmitting 1,000Hz , but not exactly the same:

Damped Sine

H-Bomb

On the other hand, Feathering creates rapid random changes in the freq being used (in the specified interval). So you will have like a "shower" of freqs in an interval of 0.02% or 0.05% from the original freq.
All this is wonderfully explained in the User's Guide, page 133 to 137.

All this functions, produce this effect on Out1 and/or Out2. If you use a boost device, you'll simply combine the two Outs. The effect of using the boost device will depend on the configuration used. For example, if you are using Inv+Synch, you'll double the resulting amplitude.

For more details, please check the link:
https://www.spooky2.com/forums/viewtopic.php?f=5&t=8010