Ever since the patch that Riot has deployed that nerfed Twitch after his visual update, his "finishing" potential with his Deadly Venom isn't as strong or potent as it used to be to people in Gold and below along with his other abilities and base. For a clarification, he was strong in ranked teams where lane swapping was common while his mid-game was somewhat strong, and Riot took notice of it and nudged Twitch with the hammer. This concept has nothing to do with his Ambush, Expunge, or Spray and Pray, since I already think they are in a balanced state already.
Twitch's Deadly Venom was the one that probably took the greatest hit if you didn't already used his Ambush as a getaway tool. All round numerically, the true damage it does early-game now is half as strong while his late game is trivial. With buffs rendering obsolete quite some time ago, it had also transitioned Marksmen to carry it now instead of (thank you bonus movement speed for also making it offensive...), which isn't temporary, further hampering the finisher of Deadly Venom. Not only that, but Kalista is often seen as a "better Twitch" solely because of her E being superior in every form compared to the original antecessor while being able to kite.
The first passive focuses more on being balanced and overall healthy in his early and mid-game while being strong in the late-game phase. However, it comes with the drawback of now being limited to 5 stacks (but can be detonated earlier now with a stack less). Twitch's early game passive damage will be just as mediocre as live, but his late game damage will as potent as his old values, if not more if he so chooses to build more pure AD, but this sacrifices his overall DPS if so chooses to do so (recommended build suggests Shiv, Whisper, and BotRK, which have little to no AD).
The second passive option is just like the first, except it retains the 6 stacks along, a base, and is dependent on his bonus AD. It slightly does more damage in the late-game phase than the first option, but is now more dependent on his item choices. Jungle Twitch would suffer a lot more from this than the first, as on-hit effects is more favorable than AD when building around a such as , , and .