How does this interesting fight play out? You have the smooth technical boxer-puncher against the flashy, erratic boxer-brawler. This would have been a cracking fight since both guys were skilled boxers and aggressive fighters who can slug it out when they want.
Canizales ought to win imo but there's always the chance he could be thrown out of his comfort zone by Tapia's aggressive speed, or lulled into a slightly nicey nicey stupor if Tapia opted to box in a more disciplined manner.
Johnny could outbox OC on a bad night. However, I sure as Hell can't see him beating the OC that lifted the title from Seabrooks and annihilated Hardy in the rematch. Tapia would get beaten up assuming those versions.
At 118, Canizales moved better than Tapia, hit harder than Tapia, and was harder to hit than Tapia. Tapia was a much better fighter before his long layoff than he was afterwards. When he returned, he fought too often with too much emotion. He was certainly still very gifted and very skilled, and he could win this fight, but it would mean catching Canizales on a bad night and Tapia on a very good night.