I think J’s jazzmasters are all equipped with the original pickups, except for the blue one with the tortoise pickups.
Seymour duncan has some nice replacement pu’s for jazzmasters.
Jazzmaster pickups are NOT P90’s. p90’s may appear similar, but they are NOT put on Jazzmasters. Jazzmaster pickups have a very low output and are very trebely. p90’s are high output and are kinda chunky sounding. J might say p90’s are his favorite pickups, but I don’t think he’s replaced the pickups on his jazzmaster, you can just hear he hasn’t