It will not trip Knox.... And you must flash back to old ncg kernel through Odin then use towelroot and then update to the ne9 kernel again through Odin... I just did this on Sunday.. There are a couple of videos on YouTube on how to do this... And yes this IS for the verizon s5
Currently towelroot will not work. I installed the Verizon update the other day and also lost root access, and towelroot gives an error message. I'm in the same boat as you.
I found this video which claims to achieve rooting after the new update.
Since I'm relatively new to rooting, can someone smarter than me confirm that I understand what is being done in this tutorial? If I understand it correctly, the steps outlined are:
1) flash back to the previous kernel / system status since before the update
2) root using towelroot
3) install the current kernel