Great question!
A feather and a bowling ball will fall at the same rate in a vacuum. This has been proven on the Moon and inside NASA's large vacuum chamber.
Hammer vs Feather - Physics on the Moon
Watch A Bowling Ball And Feather Falling In A Vacuum
In air a light ball and a heavy ball of the same size but different mass will fall at different rates. Each will have the same air resistance but the more massive ball will have more downward gravitational pull You might need some modest equipment to prove this but it is doable.
RE: Scaling - Why Ants Bounce But Elephants Go Splat