You will start with your level (min 30), equipment & skills, but not potions/oils/quest items/books ~ bascially the stuff you *can* throw into storage already. Not sure about ingredients, but as you cannot store them, maybe not... so consider cashing some or all of them in before restarting.

The witcher sets 'start again' with higher stats on the diagrams during NG+, but you can continue using the old crafted items from before the restart. I'd guess that you lose the crafting diagrams too, so only have the items already made.

NG+ items are stronger than Base level, so NG+ basic armour has more armour and resistance than Basic Mastercrafted.



My personal feeling is that it is totally unnecessary and if anything will make 'level up to become invicible' worse than it already is. I don't grok the need for NG+ and it fails to honour the lore (which is that Geralt is already at the peak of his game, and apart from a few minor items and information has no need of development ~ and that honouring this would also make 'balancing' the world internally and against Geralt much easier).