I was travelling in J. The carryon limit for J/F is 2 pieces at 18kg total, vs 1 piece+1 personal item at 12kg total for Y. For checked bags US-Asia you also seem to get a slightly higher dimensional allowance (158cm total per bag in F/J, vs 273cm total for both bags in Y), though still the same 2x32kg. Anywhere else in the world, of course, is the standard 20kg/30kg/40kg for Y/J/F. (Even SYD-ICN-NRT: the "Transpacific Region" note on the website is misleading; any chance you could mention this to someone who might be able to clear up the wording?)

For what it's worth, Air France didn't give me any problems taking my ~5kg camera backpack and ~5kg laptop bag aboard intra-European flights, despite stating "1 piece maximum" with no mention of personal items. I was kinda worried there not having flown them before, and seeing very few people with the usual personal items you see elsewhere.