Exactly, widgets are just groups of components. I call them modules now. About tutorials on Sketch symbols and their structure I would recommend you the same with naming as there is no other way to give it proper structure. Also, I’m applying new resizing features to all symbols now. For more info check links below.

http://www.sketchtips.info/articles/the-power-of-symbols
https://medium.com/sketch-app-sources/sketch-39-resizing-cheat-sheet-feec0450e7e2#.due9cr2jo