I havent found a theme yet that allows for the restraint of the bar width. Maybe OB just cannot do it yet? I'll keep trying
I don't think that the two autohiding bars are possible yet either. I think I have tried just about every combination possible to acheive the affect but If any of the developers are reading this then here might be a good place to put it
Under Theme Editor: Item-> Behavior -> Popup Properties
The ability to set the "Popup Direction" to "Down and align below item" and
"Up and align above item".
Objective: If you have a standard "Windows Style Start Bar" with a button
that launches a second full screen-width bar/popup this would allow for the
launched bar/popup to open up underneath the top bar pushing the top bar up.
When you hide the launched bar/popup the top bar would lower back to the
bottom of the screen seeming to push the launched bar down and out of view.
This would also work if you have your bars docked to the top of your screen.