Jesse goes to meet Walt...is paranoid, after all, he is going to meet "the devil". So, when he sees the bald toughie, his reaction seems right. But then the very next moment he talks about coming after Walt where he "really lives". Is that simply anger talking, or does he have a concrete plan? Apparently he does, as he tells Hank later about his "better way" of dealing with Walt. But this transition from paranoia to "eureka!" seems like a stretch.
Jesse is clearly not the thinking type, though he does come up with brilliant ideas now and then (e.g. using a magnet/ building a battery). The question is does he indeed come up with an idea to deal with Walt in those two or three minutes, when he was seemingly focussed on locating any possible threats to his own life ("clock tower guy", "poisoned needle")?
The ricin revealation in the previous episode was quite in character. He had been brooding for quite some time....turning over all the events in his mind again and again. So, the chance sighting of the cigarette pack and the missing dope, and Huell, all lead him to that one conclusion, that Walt did indeed poison Brock.