No real issues. The lower you go the more offset the axle will be from center. Lower it 2" it's not even noticeable. Lower it 3"+ you probably will want to get the aftermarket adjustable panhard bar to get it back to center. It could cause premature bushing wear in the 4 link otherwise(not to mention looking a bit funny off center).
All ram 1500's basically have the same suspensions the differences only being springs, shocks, and sway bars. Geometry and all is the same on all.
I know the reg cab express doesnt have any bars or links
Not sure what you meant by this?