I believe they said in the livestream that the hitcheck only needs to cover, say, where you want a person to be able to click to select the object, and how you want the object to snap onto other objects in the scene. Peeps in game ignore the hitcheck and will walk straight up to (or through) an object unless you use one of the special barrier pieces.
The hit check box, from what I can tell, only affects placement of scenery near rides. There is a seperate hitcheck (that we dont have access too) that is on a select few items in game that effects peeps path finding. Namely, the barriers, kerbs and that one random plant pot!
So in other Words:
If you made a 1x1x1 Meter Cue with a 1x1x1 Meter hitcheck and Place this Cube directly on the Path (Walkway) then the Peeps will walk around this Cube?