I've been ovo-lacto veg for 22 years. I didn't eat much meat before that (too poor) so it wasn't a big change for me.

Before a race, a couple eggs and whole wheat pancakes or oatmeal. Or grape nuts and yogurt and fruit.
During: rice muffins from the Allen Lim book, or Lara bars. But my in-race food limitations aren't from being veg, they're from having a sensitive stomach and food allergies.
After: anything with protein and carbs in it. Rice & beans burrito is good.

I agree that it's not rocket science. Often I make food that'd have meat and just leave it out, or use one of the fake meats that are decent. Some are tastier than the real thing (according to my wife who is not veg). I didn't much care for real pepperoni on pizza but fakeroni isn't bad.

I don't think that it makes a difference for racing but like I said I wasn't a big meat eater before. I've had friends try it and just go nuts trying to deal with it. It's probably not worth that. And it does make eating out a bit more difficult.