The 'wave' washer is supposed to go right under the nut, but really, it doesn't make much of a difference.

The 'bevel' washer is similar to the first pic you have there, with an edge that has the angle on it to fit up against the little curve on the tensioner.

But, you should be OK. In fact, if you don't want to replace the stud, you don't have to. At the dealership I used to work at, we never did unless the customer wanted it. Never, ever, had an issue. Courtesy sells them with the kit, but that's the first I've ever seen it, was when I installed a Courtesy kit on a friend's Frontier. After that, if it was there, I did it, if not, it was up to the customer.

I think you'll be OK. But if you're bored one day, I enjoy a good t-belt tear down. My fastest time was 1.75 hours, not including warm-up and bleeding (on my own Xterra, I was always fiddling with it).