The only thing I would aska bout a 20 x 30 print from 35mm is that this would be a 30X enlargement. Regardless of film, your lenses are going to really struggle here! If you are using a 35mm lens at f22 for a landcsape, diffraction will limit your resolution somewhat. Surely a 30 x enlargement of 40 lpmm will not give an exceedingly large print in real terms??!!!
I could see that gigabit, aside from any unique look that it has, would suit creamy subject matter to be blown up really large, such as foggy scenes, water scenes perhaps, where is enlarging big from 35mm would otherwise produce grain harming a dreamy effect.