my suggestion, stick with 8.5 x 11. it’s easy to carry, easy to print and easy to mail, as long as it is well organized and clean, it will impress people.
sketches and renderings tighten up and look a whole lot better when you shrink them down a bit. people like to see the complete story of how you got to your final design. show process! it doesnt matter if you can sketch like freakin chip foose, if you cant show how you think, you’ll sink.