It’s been a while, but I believe there is a priority queue for J? It’s the standard security process, with an added passport check to confirm you have a visa and can enter the US.

How early depends on when one wants to get on the flight - either at the very beginning, or at the end so as to maximise time in the lounge. probably getting there 30-45mins before departure should be fine; I doubt they’ll close the doors if you are in queue for security 20mins before departure (the stated time gates close).