The 220V spindle affords an ER-20 collet system, and more torque/horsepower, so faster material removal rates, and is more easily able to arrive at a given surface finish. The 110V is capable of a similar level of work, just it may force the use of smaller tooling/take longer/more effort to arrive at a given surface finish.
Correct, since all sizes of machines were available at launch, there is no upgrade option (which would require replacing much of the machine.
Yes, this is known as “tiling”:
Carbide Create imports DXF and SVG files as 2D geometry, pixel images may be imported to a background layer for reference/re-drawing, or auto-traced:
Carbide Create Pro adds the ability to import pixel images as height/depth maps, or 3D models as STL files: