Moriearty – I don’t recommend a 100K pot for the Reutz mod. I’d stick with the 100R pot.
I’ve played around with the Reutz mod a good bit and find it really does make a difference. IMO, using a 100R pot in a custom expression pedal would garner the best of several worlds for the Reutz mod. A custom expression pedal with a 100R pot allows the foot to sweep across the 100R value for an interesting Rat build. Kinda like a Rat-Wah.
I never did do up a custom expression pedal. But I did find that if I really want to have a settable Reutz mod, an external 100R pot seemed best. That way, I could easily just tweak the Reutz pot. 100Ω is not much of a sweep. But in the Reutz mod it really does affect the tone.
You can do the Reutz mod anyway you like. I just think having a Reutz pot and a toggle switch is redundant. The switch does the same thing as turning the Reutz pot, if installed.