There are no short cuts to fully understanding the differences. The manual is very good, but is more down in the technical weeds. Start with something more like this, and then work your way up: http://www.erareplicas.com/brochure/427sc.pdf and this http://www.erareplicas.com/427/427options.pdf Note that the latter price list is almost six years old, but still very informative.
Wait, that option list on the website is not current? But my budget...
The manual is very good, but is more down in the technical weeds. Start with something more like this, and then work your way up: 
Threaded Mode
