The LaserBoard, using LightBurn, allows you to do many things that you are unable to do with the stock board. It can automatically change power settings for you so you don’t have to stop, adjust power and then start your vector engrave or cut. You can do multiple power levels in one engraving session using different colors to specify how you want each task performed, (called layers) there is a grayscale function that allows you to perform 3D engraving and for most things you normally do, you won’t need Inkscape. If you should, however, it can import regular graphics files, Inkscape files, DXF, PDF, Adobe Illustrator files and various other vector files.
Not sure what speed you are looking for, but you have to realize, a K40 is a lower end system and going too fast will wear it out quickly, so it’s generally a good idea to keep it at 300mm/s or slower. I prefer to go 200mm/s for most projects, but have tested the LaserBoard to 550mm/s, although, I wouldn’t do that regularly because my machine would fall apart. There are two firmware versions used in the LaserBoard, one is called Smoothieware and the other is GRBL-LPC. Smoothieware is currently limited to around 100mm/s, although there are rumors that someone is working to get it moving a lot faster. GRBL-LPC can be used to about 300mm/s for normal use and much faster by tweaking the config, but I don’t recommend it for a K40 because any faster and wear and tear will be dramatically increased.
Check out some of the videos from the beginning to recent. LightBurn has come a long way and they are continuously improving it!