I have a couple females that came from a stripe x stripe pairing that look nearly patternless or very close to it; I say nearly because in person they look patternless, but with a camera flash you can make out the tiniest hint of a stripe. I will be breeding one of those females this season and another next season; hoping to prove out supers! But I’ve been breeding stripes since 2013 and always get a wide range of stripes from “aberrant” (messy stripe), granite (side patterns), regular stripe (your first pic), pinstripe (what I’ve been calling those with a very thin and clean stripe), and (nearly) patternless. The stripe to stripe pairings give the cleanest stripes in my opinion and you are more likely to get the pinstripe or patternless. With just one parent as a stripe, you get a mix mostly looking like the two in your pictures. With such a wide range of stripe quality, I am inclined to think it is poly-genetic.
Here is my girl Sylvanas, a patternless and nearly spotless Snow Paradox Stripe.