Tai Tuivasa is faster than Derrick Lewis, even though he got that body figure and built he manage to pulverize Lewis and KOed him, but Yes Cyril Gane is much faster than Tuivasa, and judging from their fight IQ, I will surely bet for Gane to win it, Tai Tuivasa has a tendency of just pursuing a KO and will surely punch without any care, while Gane is a technical fighter,
Depends what you mean by fight IQ. Gane has very good movement so in those terms he's quite exceptional given his weight class. However, that Ngannou fight he didn't display all that much fight IQ, especially when it comes to versatility. I mean, I still can't get over how he basically got dominated on the ground, when a lot of us before that fight would've had Gane being the better of the two on the ground. Simply, since Ngannou doesn't have a long history of mixed martial arts, in fact he's relatively new to MMA.
I have my doubts about Gane, and I think Ngannou exposed that side of him. Whether or not he has the heart too when the going gets tough. Tai will bring the heat, but Tai is relatively slow, and quite hittable, which suits Gane down to the ground if you ask me.