I have ridden the Seattle to Vancouver and the only big hill I remember is the one coming into Vancouver! Wife has an Osprey pack (REI) which has a camelback built into it. Pack is just the right size to stash leg and arm warmers and rain jacket after it quits raining (usually august!) and the sun comes out. I use a waist pack that I got on an STP (Seattle to Portland) many years ago. Racks and packs and water bottles are just not necessary on these types of rides.