In AutoCAD your Model Space tab *is* your model. That's the building or site plan or object of whatever that you are drawing. Layout (also known as Paper) Space is what Autodesk uses to help you print/plot your model. Within the Layout (Paper) space you create Viewport(s) to see portions of, or all of your model. When you plot, you plot from the Layout and you'll get whatever you have drawn there.
On the Layout tab, and within the plotting area, you can include anything in addition to the model (as seen through the Viewport) that you might like. Typically we will put a title block here. It only shows on this tab (or other Layout tabs) and is not part of the Model. So it only shows when you print/plot.
A DWF file is simply another type of plot. You can plot to a printer, to a plotter, to an Adobe PDF file, or to an Autodesk Design Review DWF file. So the long answer is, "Yes". Your model (all or parts of it) plus whatever you've added in a Layout can be plotted to a DWF.
Hope this helps.
Dave Hein, P.E.
It depends on exactly what you mean. If you mean plotting the model tab and a layout tab on the same sheet of a dwf file, then no. If you mean on separate sheets in the same DWF file, then yes it is possible. Plotting model space, typically involves adding a viewport to a layout and scaling it. Then plotting the layout full size.