Fun fact, if you start with 212 and end with 212, you actually get less damage than if you had ended with b12. Any other time 212 will do more except for this one starter. I haven't found much use for the other two you mentioned outside of catching someone off guard due to unfamiliarity, but it'll usually only work once. You can catch a really bad player off guard by doing b12d3 and then next time around doing b12xxbounce cancel... but this shits useless.
Actually no.. b1 is actually not a bad whiff punisher if your opponent is too close and you think B2 might get stuffed. I use it sometimes on a backdash against Superman if my timing is off and he's closer than I want him to be.
Most likely these strings would have some use on kd for setup, you might be guaranteed a dash up meaty grab or dash up njp to beat certain wakeups. I haven't really labbed these strings though so feel free to prove me wrong