I’m no 100 mile veteran, but I have studied aerobic vs anaerobic training a lot. The more you stay in Zone 2 during your race, the less glycogen you will burn, the more fat you will burn instead, and you’ll be feeling good for a long time. Only There is much less lactic acid being produced when you stay aerobic, and you’ll be tapping into the big energy of your fat storage. If you train your aerobic capacity and build it up before the fall, you will likely be able to run pretty fast without going too far into Zone 3, but I guess that depends on how aerobically deficient you are.
I know some people who have done very well in 100 milers, and after seeing their data, they stayed in Z2, with only a few occasions going into Z3.