features i'd like to be able to customize in EFR's enchanting system:

the max amount of levels for an enchant (i'd personally set this to 50)
the amount of levels enchantments take (i'd set this to 5), maybe the max level enchant could take 10 instead?
the amount of bookshelves to reach the max level enchantment (i'd personally set this to 30)
ability to turn off enchantment previews in the config