Wasp VCFs are great for leadlines...they have a very cutting sound that rips right thru the mix. Feed that something that's harmonic-rich (sawtooth, perhaps) and it'll shriek and yowl like the best.
The Three Sisters, though, is a different critter altogether. What it is is something between a bandpass filter and a formant-emphasis filter, which is useful for synthetic vocal sounds, which are usually the vowels as they contain all of the fundamental and formant spectra. But if it's not being produced (the listing doesn't show that as it's manufacturer-locked), there IS an alternative: https://www.synthrotek.com/limaflo-motomouth-formant-filter-eurorack/ Synthrotek's distributing these now, which I and others might consider problematic, but that's more or less the only game in town that'll get you into the Three Sisters turf.