If you're rendering for DVD Achitect, my advice would be to use one of the MPEG2 template that SAY DVD Architect ... you can choose 24P, widescreen, etc.
I always use the default template, and then ensure my render setting is at BEST, and typically put it on 2Pass, just to make sure it catches everything.
Otherwise, if that were to fail for some reason (i.e. you're over two hours of video), then I'd render that thing out to an uncompressed AVI (SD size), and then use Architect's "Fit to Disc" option, when optimizing your DVD. That'll work, guaranteed, as it'll render it down to the size of MPEG you need to make it perfectly fit on the DVD. Another note: I've noticed that when trying to fill a DVD beyond 94-96% capacity, there tends to be errors, so don't try & squeeze more than the "Fit to disc" wants to default to.