How does new game + work?

[Inferior]

I have been playing the game and as usual I want to do all the possible stuff on my first playthrough.
I got to a special grave and when I checked online about it it said that if I beat a boss before arriving here I get locked out of the Wounds of Eventide DLC quest which is apparently important for the true ending.
So I guess I will have to retry it on a second playthrough.
I wanted to ask how the new game plus works in the sense of what is saved, what items I keep and which I do not keep, do I have to re do any quests, etc.
I do know there is also new content unlocked on new game plus. Some special bosses if I remember correctly? If anyone who is familiar with this can make clarifications I would be grateful

[Hotel Security]

You keep your spells and beads but then lose your health and bead slots and have to recollect those. Enemies are also a little tougher with more damage and HP but they're all probably easier since you can spam your best spells each fight. The run is much quicker, however, since all your travesal abilities will make it so you can collect everything in an area on your first run through. You can redo all the quests though I don't know if you have to.

And yes, there are the Amanecidas which are bosses only available via NG+ and those are some fun fights as well.