I keep my male in a 4ft long tank with a wooden lid. But we are upgrading to a 5-6 ft as soon as money permits.
IMO, (and from my personal experience with corns) corns are very active snakes and you will often see them exploring their environment.
Comparing them to royals is really not vaulable, as royals are not active snakes at all.
As babies, keep them in small tubs (not glass tanks as glass tanks will provide too much himidty for them at such a small size) and upgrade. Putting a young corn even in a two foot glass tank/viv or tub is far too big. These snakes are very slim, and tiny and will stress out. Provide plants and hides in the small tub as a baby and upgrade as needed. For an adult corn snake of 4ft or bigger I personally believe a 5ft enclosure is minimal, whilst I will have arguments about this, I'm talking in my opinion and experience which will not change. These snakes are the most active of all my species I've kept.