Incline tricep extension is the best exercise for the long head of the triceps.
Ohp and bench do nothing to target it. I 1/2/3/4 pl8, but never felt DOMS in the long head before isolation long head with 5kg dumbbells.
The long head of the triceps is connected to the scapula. So to target it you need to have a stretch in the tricep while doing it.
TLDR; incline tricep extension is GOAT