JAL has 9 across on their domestic config 788s (which is a ~3 hour max longest route with the majority of Japanese domestic routes in the 60-90 min range). All their other 787 configs are 8 across.
The JAL configs vary across the fleet. Some don't have premium economy, some have a larger business cabin.
788
E21: 6F 58J 227Y (Domestic)
E12: 30J 156Y
E11: 38J 35W 88Y
E03: 30J 176Y (previous generation seats)
789
E92: 28J 21W 190Y
E91: 52J 35W 116Y
E71: 44Y 35W 116Y
E12, E11 and E71 have "JAL SKY SUITE"
E92 and E91 have "JAL SKY SUITE Ⅲ"
The W and Y seats on those configs are the same.
The QF 789 has 42J 28W 166Y with 12J 28W and 42Y between doors 2 and 3 and 124Y in the rear cabin behind door 3.
JAL 789 has 116Y behind door 3. E92 has 21W and 74Y between doors 2 and 3.
In the same space Qantas has 124 seats, JAL has 116.
This is the JL Y seat used on their 787s (except E21 and E03 configs)