I assume that the different Solutions are based on different regulations in different parts of the world.
Some Solutions would not work here in Europe, due to limitations on check-in etc etc.
Rig sizes changes your possibilities drastically.
My wife has a M4/3 System and she packs everything ( except arms and handles) in a reasonably sized Camera Backpack.
I need to pay much more attention to my Fullframe rig.
Camera and a Lense in the Housing + Flatport, wrapped in Neoprene and carried in the Lanyard
Domeport and Lenses in a Backpack => Looks reasonably sized, but is heavy.
The rest is checked-in.
It is very uncomfy at the Airport, but I have never been checked. I have seen a lot of People with rollers being checked.