Ng + will give exp not for the quests but if you fight mobs while in it. I tried that out with my drg. However that's the only exp I've gotten so far in it and that was just killing the mobs out in the world. Havent hit a dungeon yet.

I unlocked ng + yesterday before going to bed after I completed the msq. Started Shb again and I am enjoying it when I play around in it, so yes I'll be using it more just gotta finish the Nier raid now.