You have already heard that the Popular has three seats up front and the Versatile has four. In the Popular on the driver's side there is a wardrobe cabinet behind the drivers seat instead of the fourth seat in the Versatile. The bed is longer in the Popular and you have the option to sleep side to side or back to front - not in the Versatile in which the bed is side to side.
The inside is the same regardless of the windows - the solid looking windows are black paint between the windows.
While all 190s are on the Chevy 3500 chassis SINCE RT stopped using the Dodge in early 2000s - not all 190s have the 6.0L engine which was an option until recently. So you could get the smaller Chevy engine in a 190. Check the VIN which will tell you both the specs and the chassis year. Roadtrek builds, for example, a 2009 on a 2008 chassis and also on a 2009 chassis - depending on the time of the year the Roadtrek is built inside the van when which chassis is available from Chevy.
See my site linked below to learn all about the Roadtrek 190 Popular.