The current Glowforge post processor just creates an SVG. It does include kerf compensation if you set up your “tool” to have the correct kerf. However, it does not color each operation differently. So, you would still need Illustrator or Inkscape to separate out each operation.
I admit that the post is not ideal. When it was written, the Glowforge people were too busy trying to deliver units to help us. If you recall, the product was a tad bit late to market…
I like @gareth 's idea of a custom post that would color each operation differently. If that worked, you could go straight from Fusion 360 to the Glowforge web interface and skip Illustrator or Inkscape entirely. That is assuming, of course, that your design includes vectors and NO bitmaps. If you have bitmaps, you will surely have to use Illustrator or Inkscape. @gareth, if you write the post, I’ll help you get it into the Fusion post library!
In the meantime, I save out my sketches as SVG files and then import into Illustrator. I do not ever have scaling issues because when I import, it asks me the units and the scale. I choose mm and then make sure it is set to 1:1. The result is perfect every time. In Illustrator, I lay out my parts and color my operations. I am using a template that is set to the max size I can cut in my Glowforge. My template also has 9 different solid colors I use to separate everything out. The colors are set to be visually distinct, which is why I only have 9 or so.
Hope that helps!