PJ is a large area, a coupon taxi from KLIA, would be the fastest way but there is a 50% surcharge from midnight.
Or take grab taxi. I believe there is no surcharge for this one but you need to get a local sim card or use the wifi from the airport to book using the grab taxi app.
It's faster to take a coupon taxi or grab car.
Buying your KLIA express ticket, waiting for the KLIA express train, taking the train for 30 minutes, getting a coupon taxi at KL Sentral and driving to your PJ destination will most likely take over 1.5 hrs. Also if your flight gets delayed, the last KLIA express ends at 12:55am.