re: When I am creating walls for a second floor, where they follow walls from the first floor, they don't show up properly.
You should draw the walls at the proper height between each other. If you draw your first floor on the World Workplane (0"), then you would need to draw the second floor on a new workplane, say 120" above the first floor. I would click on "Plane by World" first (Pop-Up Toolbar)(just to make sure I'm there), then click on "WorkPlane Origin". Shift+Tab to the Coordinate fields and enter 0,0,120. If you use the Grid as a visual aid, you won't notice any shift when switching between workplanes. Now that your second floor is being drawn 10 feet above the first floor, you shouldn't experience any interference marks.
Designer, Deluxe, (Professional, Expert, Basic), Platinum
Windows 10 Pro (1903), 64-bit