How many items from 6 have some sort of actual usage in 7, and how many are just allowed to transfer? By "usage" I mean like how the diamond ring can cut through glass, not just weapons like fang that are handy.

If you received a certain token from Rebecca (assuming you didn't kill her) then hang on to it. It won't be relevant in Wiz7 AFAIK, but it will have a use in Wiz8.