They will all need regular upkeep, though putting down weedblock will be the most effective at controlling the weeds. Rocks without weedblock would be inviting the weeds to proliferate. The size of the rocks is purely a personal preference, I would use the smaller rock because it will provide a smoother walking surface. Wind blown dirt and bird droppings will eventually build up above the weedblock and provide a medium for the weeds anyway (may take a few years), so regular maintenance will be needed no matter what is used