You can view 3D DXF and DWG files in ArcGIS natively. No conversion necessary. You can also import all features into a geodatabase or shapefile.
As for the data format, if there are polylin and polygon features in the 3D model, you can export these to ESRI Shapefile or Geodatabase Features Class but the 3D Solid objects can be converted to ESRI 3D Multipatch Features.
Textures and colors might not display correctly.
ArcGIS 3D Analyst applications (ArcGlobe and ArcScene) are not exactly meant for viewing building interior space but I can't see why it couldn't work.
It seems to me that Google SketchUp might be better suited for this type of visualization but you will need to get the PRO version to import DXF and DWG. Even in ArcGIS we use it to construct building exteriors for our scenes. The last time i checked, Google was offering a free 48 hour trial.