^ Nothing carries over, you just start at level 90. The difficulty is the same.
Same for New Game-. It's a clean start but you stay at lvl 122333 (Vaan, Fran, Balth, Basch, Ashe, Pen.) You get New Game- after finishing stage 100 of the Trials.
(Or, just don't kill any mobs until you equip Firefly's, same thing
)
Re: New Game+, I went back to my old file instead because I wasn't going to play through the whole game again and doing all my hunts and getting all my weapons etc. My main party is at lvl 65. Took down Fafnir at ~60, it was a bit of a pain but Ice Shields + Bubble Belts + Reflectga Motes + Thundaga = OP. I want to try finding better weapons and equipments next - my experience with this game has always been that armour and weapons (and strategy) are more important than levels.
Oh, and since I'm a sucker for that PS4 Plat... I've decided to carefully plan out my next roles in order to get the Magick and Technich trophies. I'm not even sure I can get them all, I have 8 Technics I need to unlock, and I don't really want to waste Espers on getting them. Soooo... next stop: Research
Edit: Okay that was just 2 Technicks and I can unlock them both by getting a Monk.
Also, for the Magick trophy I need to get a Time, White and Black mage because those are the only 3 jobs that can learn some of the abilities. Hm. That leaves me with two more jobs to choose from... I really do want a Samurai/ Bushi, but the Shikari is really nice so I might get a second of those.
What to do...
I guess I need to choose jobs for my 3 main party to make them ready for the tougher marks. Say for Omega Mark XII, if Ashe had the Samurai job as well she could just wack away while Fran and Basch supported her with Decoy and Reverse. Only problem is, they're both kinda slow, so I should preferably give jobs with those abilities to Vaan and Balthier. Reverse is standard for both Black & Time Mage, Decoy for all mages.
Balthier the mage... hm.
Oh and
this list is pretty nice. Pretty sure it was listed before though.