What changes in New Game Plus?

According to the developer's website, the game has a New Game Plus mode. However, I can't find any information about it.

Are there any additional areas or anything like that? What changes are there between NG+ and the normal game?

In New Game Plus I have observed the following changes:

• you earn 5 extra gold per coin (50 for money bags and 250 for diamonds.)
• Enemies are all evolved by one (Where Skeletons were situated in the first play through, Mr Bones takes their place, same with Archer/Ranger, GuardBox/GuardBox XL, Doomvas/Doomscape, etc.)
• New blacksmith plans can be found.

New Game Plus 2 has the same gold (an extra 5 gold per coin, etc.) and enemy changes (GuardBox XL becomes GuardBox 2000.)