The first of these fast-moving worms is almost like a caterpiller in that it appears to have feet (if you look closely at the photo); however the second most definitely does not and is therefore more worm-like.
Both of these creatures like damp conditions (I actually found the long, really thin, one in a puddle outside of the back door at the bottom of the garden after heavy rain), and hate being videod and photographed on tissue paper.
The shorter, more caterpillar-like one, also has a slightly flattened and very shiny black torso, whereas that of the longer worm was more of a matt colouration with a round wire-thin body.
The first (and considerably shorter worm - if that is what it is) can often be found munching on earthworms and in burrowed-out craters of wild strawberries, but I am uncertain as whether it kills the earthworms, germinates inside of them, or what. The second I have only ever found one of (that in the photograph).