A trim pot with each of the 1 nF and 2 nf caps - that could work! Possibly a series combo also! I have seen a tester using a trimpot to dial in the best resistance for different value capacitors. They are available.

As for my tested options - Yes, I could hear a difference between my various parallel options. I only tested with Mr Scary though!

I did not try the cap in series with the resistor. I will try that and report back. I have a build with muddy humbuckers - I had planned to try a smaller capacitor on the tone (as I thought the cap values where 100 nF (not 47 or 22!))

As for "How much difference do you hear using the different tone-bleed circuits that you can't adjust for with the tone control?" I'm not normally a big tone control changing fellow. But I will give it a go!

As for middle of the road - yes nothing to radical for me!