Fun fact, Jim Kelly ran that offense in the USFL prior to coming to Buffalo under OC "Mouse" Davis and there were some concepts from that he brought to the K-Gun offense as well.
Defenses figured it out and there were too many protection issues and the QB's ended up taking an awful beating by the end of the year...but some concepts for sure have become mainstays in the "spread" offenses we see today, just added different personnel packages to run them out of.
Here are a lot of Run 'N Shoot playbooks from actual teams and OC's that ran them if anyone likes to geek out over that kind of stuff like I do...it includes the playbook Kelly would have run with the Gamblers in the USFL.
Looking at these sometimes makes my head spin with the amount of knowledge these players must both memorize and be able to recall instantly at any given time. "Dumb" football players aren't really a thing.
https://runandshootoffense.com/playbooks/