Hey guy, first and far most... Your plant looks nice and healthy so good job!
It is too early in your veg cycle to tell the sex. 2 options for you, cut off a clone and put it into 12/12 to force it to show sex while leaving the rest of the plant to continue to veg, or just change the light spectrum now and go 12/12 but your yield will be smaller since you won't be vegging for very long. And to answer your other question, yes your plant will grow greatly once you switch cycles to flowering, almost 3x growth increase on average.