If you're racing then I recommend GPS and maps. GPS is pretty reliable, but like any tech device it can stop working and if you don't have maps (or a backup GPS, which is what I do) then you are really sunk. If you are racing it is cheating to ask directions from other racers or tag along with them while they do all the navigating, so you really need to prepare as if you'll be out there by yourself.
I'm also going NoBo, though I'm touring so I can be relaxed about the rules (and I definitely plan on accepting meals from anyone who offers ha ha!). Nonetheless, I'll be taking two GPS units (etrex 30) plus maps and a bike computer. As other folks have mentioned some of the cues are a bit slippery. I've lost track of how many bikepacking adventures I've done where the cue was something like "bear left at the fork" and when I got there there the road split into four sections with three of them bearing left. Uhhh . . . .
Glad I had the GPS!